In our research, we systematically study the polarization-resolved nonlinear dynamics of a Vertical-Cavity Surface- Emitting Laser (VCSEL) under both continuous-wave (CW) optical injection and 3-line gain-switched (GS) optical frequency comb (OFC) injection, applied orthogonally to its parallel polarization. Our results show that the nonlinear dynamics induced by GS-OFC injection are determined by two factors: (1) the frequencies of the nonlinear dynamics of the VCSEL under CW optical injection and (2) the polarization switching curves for both types of optical injection. Both factors are essential in understanding the physics of the OFCs observed at the VCSEL output. We demonstrate OFCs with approximately 50 GHz width.
The field of nonlinear optics (NLO) has been continuously growing over the past decades, and several NLO data tables were published before the turn of the century. After the year 2000, there have been major advances in materials science and technology beneficial for NLO research, but a data table providing an overview of the post-2000 developments in NLO has so far been lacking. Here, we introduce a new set of NLO data tables listing a representative collection of experimental works published since 2000 for bulk materials, solvents, 0D-1D-2D materials, metamaterials, fiber waveguiding materials, on-chip waveguiding materials, hybrid waveguiding systems, and THz NLO materials. In addition, we provide a list of best practices for characterizing NLO materials. The presented data tables and best practices form the foundation for a more adequate comparison, interpretation, and practical use of already published NLO parameters and those that will be published in the future.
The field of Nonlinear Optics (NLO), launched about 60 years ago, has gained considerable momentum over the past two decades, resulting in an enormous growth in NLO publications for a wide range of material categories, including bulk materials, 0D-1D-2D materials, metamaterials, fiber waveguiding materials, on-chip waveguiding materials, and hybrid waveguiding systems. However, a convenient summary of NLO data collected since 2000 for these different material types has been lacking and would be a valuable resource for researchers in the field. Here, we present a new set of data tables showcasing a representative list of NLO properties taken from the literature since 2000 on the above-mentioned material categories. Furthermore, we provide best practices for performing and reporting NLO experiments. These best practices underpin the selection process that we used for including papers in the tables, and also form the foundation for a more adequate comparison, interpretation, and use of the NLO parameters published today and those that will be published in the future.
Semiconductor optical amplifiers (SOAs) are key building blocks in photonics. Given the large interest in the use of SOAs for ultrashort pulse amplification, it is important to adequately model the SOA operation while including the nonlinear effects taking place in these components. To increase the SOA performance, it would also be useful to have an inverse model that calculates the required input pulse to obtain a targeted output. However, to the best of our knowledge, no inverse models have been developed so far that consider the many nonlinear effects critical for ultrashort pulses. Here, we introduce a generic inverse SOA model that calculates the required input pulse including its shape and phase to obtain a desired output and that takes into account the effects of band filling, carrier heating, spectral hole burning, two-photon absorption, and the associated free carrier absorption. Our model will enable a more efficient and well-targeted design of SOA-based photonic systems, while also allowing better performance control.
We give an overview of our recent progress on the design and proof-of-concept demonstration of interfacing components for short-distance optical interconnects with a particular emphasis on their fabrication through two-photon polymerization-based laser direct writing. We show mode field conversion tapers printed on single-mode optical fibers for easy and efficient interfacing to various photonic integrated circuits, circular and square planar waveguide structures with V-groove inspired alignment structures for easy coupling to fibers, microlenses and fan-out diffractive optical elements.
We give an overview of our recent progress on interfacing components for short-reach optical interconnects fabricated through two-photon polymerization-based laser direct writing. We show mode field conversion tapers printed on single-mode optical fibers for easy and efficient interfacing to various photonic integrated circuits, circular and square planar waveguide structures with V-groove inspired alignment structures for easy coupling to fibers and fan-out diffractive optical elements. For all these components, we present the process flow from optical design and simulation over laser direct writing fabrication and metrology to proof-of-concept demonstration.
We present our latest results on the design and fabrication of mode-field conversion tapers for low-loss optical interconnects. These structures are fabricated by means of two-photon polymerization-based 3D nanoprinting. We experimentally demonstrate that our 3D nanoprinted downtapers outperform conventional lensed fibers for low-loss edge coupling of single-mode fibers with SOI, Si3N4 and InP-based photonic integrated circuits. They are also more robust as they allow butt coupling rather than free-space coupling. Non-linear taper profiles allow shortening the length of the downtapers while keeping their performance. We also demonstrate 3D nanoprinted uptapers that allow for relaxation of the lateral misalignment tolerances.
Photonic Integrated Circuits have made it possible to decrease the footprint of traditionally bulky optical systems and they create opportunities for various new and fascinating applications. One of the limiting factors for the widespread adaption of PICs is their connection to the outside world. As the mode field diameter of optical modes in waveguides tends to be an order of magnitude smaller than in their fiber counterparts, creating an efficient, robust and alignmenttolerant fiber-to-chip interface remains a challenge. In this work, we investigate the optimization of the fiber-side of the optical interface, whereas the chip itself remains untouched and makes use of spot-size convertors. Optical fiber tips can be functionalized using two-photon polymerization-based 3D nanoprinting technology, which offers full 3D design freedom and sub-micrometer resolution. We present a down-taper design strategy to match the mode-field diameter of single-mode optical fibers to the modefield diameter of waveguides with spot-size converters on PICs. The 3D printed down-tapers are characterized towards their geometry and mode shape, and we experimentally demonstrate their use for coupling towards a Silicon-On-Insulator chip with spot-size convertors. Furthermore, the performance of these down-tapered fibers is compared to conventional lensed fibers in terms of optical coupling efficiency.
In recent years the integration of graphene on nanoscale waveguides has attracted much attention as it allows using wellestablished CMOS technology for constructing next-generation photonic integrated circuits. However, important challenges need to be overcome regarding the fabrication and patterning of graphene-covered waveguide devices. In addition, a more in-depth investigation of the fundamental optical properties of graphene-covered waveguides, and in particular their nonlinear optical characteristics, is required. The latter are promising for, amongst others, generating spectrally broadband light useful for a wide range of application domains including telecommunications and sensing. In this paper we present a novel approach for patterning graphene on top of waveguides, and provide new insights in the nonlinear optical properties of graphene-covered waveguides. The patterning approach that we developed is chemicalsfree and based on laser ablation and plasma etching, removing the graphene top layer without damaging the underlying material. Regarding graphene's nonlinear optical properties, we focus on the nonlinear-refraction process of self-phase modulation causing spectral broadening of laser pulses in graphene-covered waveguides. We show that the underlying physics is not based on refraction induced by graphene's conventional third-order susceptibility, but instead on a much more complex phenomenon that we call saturable photoexcited carrier refraction.
We present the use of femtosecond laser ablation for the removal of monolayer graphene from silicon-on-insulator (SOI) waveguides, and the use of oxygen plasma etching through a metal mask to peel off graphene from the grating couplers attached to the waveguides. Through Raman spectroscopy and atomic force microscopy, we show that the removal of graphene is successful with minimal damage to the underlying SOI waveguides. Finally, we employ both removal techniques to measure the contribution of graphene to the loss of grating-coupled graphene-covered SOI waveguides using the cut-back method. This loss contribution is measured to be 0.132 dB/μm.
The tremendous progress in the fabrication of highly confining silicon-on-insulator (SOI) waveguides has been very beneficial for four-wave-mixing (FWM)-based wavelength conversion applications. Nevertheless, to establish power-efficient and wideband FWM wavelength conversion, one typically requires long (cm-scale) SOI waveguides with dispersion-engineered cross-sections that do not comply with the fabrication constraints of multiproject- wafer-oriented silicon photonics foundries. In this paper, we numerically examine the opportunities for wideband wavelength conversion through FWM in a foundry-compatible SOI waveguide covered with the highly nonlinear two-dimensional material of graphene. When combining subwatt level pump powers with a short waveguide length of only a few hundreds of microns, perfectly phase-matched conversion with significant efficiencies close to 20 dB can be obtained over a more than 40 THz-wide signal band adjacent to the pump frequency. Because of the tunability of the graphene properties, it is also possible to obtain quasi-phase matched FWM conversion through a periodic sign reversal of the graphene third-order nonlinearity along the waveguide. Conversion efficiencies exceeding 30 dB can be achieved over a 3.4 THz-wide signal band that is situated as much as 58 THz away from the pump frequency. Finally, the graphene tunability also allows for switching between the perfectly phase-matched and quasi-phase-matched operation modes.
We investigate the effect of phenomenological relaxation parameters on the third order optical nonlinearity of doped graphene by perturbatively solving the semiconductor Bloch equation. We focus on the contributions of optical transitions around the Dirac points, where the widely used linear dispersion relation is a good approximation. An analytic expression for the nonlinear conductivity at zero temperature can be obtained even if relaxation is included. With this analytic formula as a starting point, we construct the conductivity at finite temperature; and we illustrate the dependence of several nonlinear optical effects, such as third harmonic generation, Kerr effects and two photon absorption, and parametric frequency conversion.
We numerically investigate the capabilities and advantages of Raman lasers based on integrated single-crystal diamond ring resonators. To this end, we first model continuous-wave (CW) Raman lasing action while taking into account the lasing directionality, the linear and nonlinear losses, and the coupling of the fields between the bus and ring sections of racetrack-shaped diamond ring resonators. We then consider the design of the ring resonators for a short-wavelength infrared (SWIR) and an ultraviolet (UV) Raman laser. Using our Raman lasing model, we determine the lasing directionality, pump threshold and lasing efficiency of the SWIR and UV devices. We find that both can yield efficient CW operation with SWIR and UV lasing slope efficiencies of 33% and 65 %, respectively. These results showcase the potential of integrated diamond ring Raman lasers for producing wavelengths that are challenging to generate with other types of integrated lasers.
We present the design of a photonic crystal-based multilayer structure that allows to experimentally demonstrate, using attenuated total reflectance experiments, the existence of the predicted transverse electric (TE) polarized excitation in graphene. We show that this mode can be excited in a single layer of graphene, even at room temperature. Furthermore, we prove that the observed mode in the reflection spectra corresponds to the TE- polarized graphene excitation and not the Bloch Surface Wave of the photonic crystal experiencing graphene- induced loss. Finally, we point out that adding an extra layer of dielectric material on top of the structure would ensure the unambiguous identification of the TE graphene mode even in the presence of fabrication errors.
We present an iterative design method for the coupling and the mode conversion of arbitrary modes to focused surface plasmons using a large array of aperiodically randomly located slits in a thin metal lm. As the distance between the slits is small and the number of slits is large, significant mutual coupling occurs between the slits which makes an accurate computation of the field scattered by the slits difficult. We use an accurate modal source radiator model to efficiently compute the fields in a significantly shorter time compared with three-dimensional (3D) full-field rigorous simulations, so that iterative optimization is efficiently achieved. Since our model accounts for mutual coupling between the slits, the scattering by the slits of both the source wave and the focused surface plasmon can be incorporated in the optimization scheme. We apply this method to the design of various types of couplers for arbitrary fiber modes and a mode demultiplexer that focuses three orthogonal fiber modes to three different foci. Finally, we validate our design results using fully vectorial 3D nite-difference time-domain (FDTD) simulations.
In this paper, we numerically demonstrate the promise of silicon microdisks for Raman Stokes/anti-Stokes wavelength conversion. We design a silicon microdisk suitable for Raman wavelength conversion with “automatic” quasi-phase matching. We show that with this design and with a 2.5% incoupling efficiency for the pump and Stokes input, we can theoretically achieve wavelength conversion efficiencies up to 3.2 dB at input pump powers as low as 7.8 mW. Regarding fabrication tolerances of the design, we find that small deviations from the optimal cross coupling coefficient and from the condition for “automatic” quasi-phase matching are allowed without deteriorating the wavelength conversion efficiency.
The emergence of synthetic diamond has enabled photonics researchers to start exploiting the unique optical properties of diamond for various applications. In this paper we numerically predict the performance of
diamond ring waveguide structures for nonlinear wavelength conversion. After examining to what extent both
dispersion-engineered phase-matching and “automatic” quasi-phase-matching can be established in diamond ring
converters, we show that these phase matching approaches can yield high conversion efficiencies for a wide range
of wavelengths in the near-infrared/mid-infrared domain, as well as in the ultraviolet/visible domain.
Nonlinear four-wave-mixing (FWM) interactions enable a wide variety of photonic functionalities, including wave- length conversion, all-optical switching, signal regeneration, and generation of entangled photons. To achieve efficient FWM interactions the waves either have to be phase-matched, or a quasi-phase-matching (QPM) scheme has to be realized. However, these techniques conventionally require light-guiding media with specific characteristics. We propose a more general QPM scheme for enabling efficient FWM interactions in the presence of a large phase-mismatch. The scheme is based on increasing the distance over which there is FWM gain, while simultaneously decreasing the distance over which there is FWM loss. This is achieved by adiabatically alternating between two phase-mismatch values along the propagation path. We discuss in detail how such phase-mismatch switching (PMS) can be employed to achieve QPM of a FWM process, what the requirements are for optimal FWM efficiency, and how the scheme is impacted by nonlinear dispersion as well as optical losses. Additionally, we describe how QPM by PMS can be implemented with a silicon-on-insulator strip waveguide of which the width is adiabatically varied between two values along the propagation path. By means of numerical simulations, we show that such a waveguide can enhance the wavelength conversion by 20 dB after 1 cm compared to a corresponding constant-width waveguide. For a pump wavelength of 1550 nm, PMS enables efficient conversion (> -21 dB) around a target signal wavelength situated anywhere in the entire near-infrared wavelength domain of 1300-1900 nm.
The energy consumption per transmitted bit is becoming a crucial figure of merit for communication channels. In this paper, we study the design trade-offs in photodetectors, utilizing the energy per bit as a benchmark. We propose a generic model for a photodetector that takes optical and electrical properties into account. Using our formalism, we show how the parasitic capacitance of photodetectors can drastically alter the parameter values that lead to the optimal design. Given certain energy-per-bit and bandwidth requirements, is it possible that a photodetector optimized for the energy per bit would be noise limited? We identify different noise sources and model them in the simplest useful approximation in order to calculate this noise limit. Finally, we apply our theory to a practical case study for an integrated plasmonic photodetector, showing that energies per bit below 100 attojoules are feasible despite metallic losses and within noise limitations without the introduction of an optical cavity or voltage amplifying receiver circuits.
We report the first demonstration of laser wavelength tuning with a resonant grating in the mid-infrared spectral
domain and with Littrow mounting of the grating. We show for a mid-infrared Cr:ZnSe solid-state laser that this
tuning technique is much more wavelength selective than prism-based tuning, while inducing significantly lower
cavity losses than in the case of a standard metal-coated grating. Furthermore, the resonant grating allows tuning
the Cr:ZnSe laser over as much as 400 nm around a center wavelength of 2.38 μm. This shows the potential of
employing Littrow-mounted resonant diffraction gratings for controlling and tuning the emission wavelength of
lasers emitting in the mid-infrared spectral domain and other wavelength regions.
We present a generic approach to determine the phase mismatch for any optical nonlinear process. When applying
this approach, which is based on the evaluation of local phase changes, to Raman- and Kerr-based four-wave-mixing
in silicon waveguides, we obtain a novel expression for the phase mismatch which is more accurate as
compared to the conventional definition; and which contains additional contributions due to the dispersion of
the four-wave-mixing processes, the so-called four-wave-mixing dispersion. By means of numerical simulations,
we show that this additional dispersion has a significant impact on the evolution of the phase mismatch along
the waveguide, and thus on the conversion efficiency.
In this paper I present a generic model that describes the lasing characteristics of continuous-wave circular and racetrack-shaped
ring Raman lasers based on micro- and nano-scale silicon waveguides, including their lasing directionality and
polarization behavior. This model explicitly takes into account the effective Raman gain values for forward and
backward lasing, the Raman amplification in the bus waveguide, and the spatial gain variations for different polarization
states in the ring structure. I show numerically that ring lasers based on micro-scale waveguides generate unidirectional
lasing in either the forward or backward direction because of an asymmetry in nonlinear losses at near-infrared
telecommunication wavelengths, whereas those based on nanowires yield only backward lasing due to a non-reciprocity
in effective gain. Furthermore, the model indicates that backward lasing can yield a significantly higher lasing output at
the bus waveguide facets than lasing in the forward direction. Finally, considering a TE-polarized pump input for a (100)
grown silicon ring Raman laser, I demonstrate numerically that the polarization state of the lasing radiation strongly
depends on whether micro-scale or nano-scale waveguides are used.
We propose an efficient four-wave-mixing-based wavelength conversion scheme in a silicon nanowire ring whereby no
dispersion engineering of the nanowire is required. Instead, we rely on the spatial variation of the Kerr susceptibility
around the ring to quasi-phase-match the wavelength conversion process for TE polarized fields. We show through
numerical modeling that in the absence of dispersion engineering this quasi-phase-matched wavelength conversion
approach can outperform 'conventional' wavelength conversion by as much as 10 dB.
Starting from the propagation equations describing four-wave-mixing-basedwavelength conversion, we investigate
how the conversion efficiency in silicon waveguides is influenced by the frequency difference between the pump
and Stokes input waves. By means of numerical simulations we show that, by detuning this frequency difference
slightly away from Raman resonance, the conversion efficiency does not necessarily decrease, but can even be
more than doubled as compared to Raman-resonant operation. At the same time, other values of the frequency
detuning that still remain well within the Raman linewidth can lead to a more than 10 dB decrease in efficiency.
As such, we show that a high-resolution tuning of the frequency difference is not only necessary to obtain
an optimal conversion efficiency, but also to avoid the detrimental efficiency decrease in case of an inadequate
detuning. Finally, we discuss how the pump-Stokes frequency difference that is optimal for wavelength conversion
varies with the length of the waveguide and with its dispersion characteristics.
In this work we designed and made a photonic crystal structure with a photonic band gap around 532 nm wavelength.
The structure was to be made from two commercially available glasses. Both should have similar temperature
coefficients (alpha), also melting and softening temperatures should be as close as possible in order to thermally process
both glasses together. In addition the refractive indexes of chosen glasses should be as different as possible in order to
facilitate a wide band gap. The pair of glasses that met those requirements is LLF1 and SF6 produced by Schott. For
those two glasses we performed a series of computer simulations using MIT MPB software. After checking various
structures the widest band gap for the 532 nm wavelength was found for the hexagonal structure of high dielectric
constant rods in low index material with a linear fill factor of 0.12 and a lattice constant 3.75 μm. This structure was
manufactured using the stack and draw method. The measurements of the final structure made by ESM show that it is
regular, with diffusion between glasses at the manageable level. This assures that manufacture process is repeatable.
We present our latest findings on the nature and behavior of CARS in active Raman devices, such as Raman converters
and Raman lasers, which operate at exact Raman resonance. We demonstrate that the CARS mechanism in these devices
actually comprises two opposite and competing interactions, which respectively create and annihilate phonons in the
Raman-active medium. Furthermore, we show that both the phase mismatch of the CARS process and the level of pump
depletion determine which of these two interactions takes place along the fields' propagation path in the Raman devices.
Finally, we compare this CARS model with the model used by the CARS spectroscopy community, and explain that the
difference between both models is mainly due to the fact that "CARS" in the context of Raman devices refers to Ramanresonant
four-wave mixing, whereas "CARS" in the context of spectroscopy often denotes a two-step Raman interaction.
We propose a silicon ring Raman converter in which the spatial variation of the Raman gain along the ring for TE
polarization is used to quasi-phase-match the CARS process. If in addition the pump, Stokes, and anti-Stokes waves
involved in the CARS interaction are resonantly enhanced by the ring structure, the Stokes-to-anti-Stokes conversion
efficiency can be increased by at least four orders of magnitude over that of one-dimensional perfectly phase-matched
silicon Raman converters, and can reach values larger than unity with relatively low input pump intensities. These
improvements in conversion performance could substantially expand the practical applicability of the CARS process for
optical wavelength conversion.
We present a Mach-Zehnder interferometer to characterize semiconductor microlenses in transmission. We therefore
make use of a wavelength of 1550nm with the possibility of expansion towards the IR spectrum. In this paper, the
concept of our interferometer as well as the set-up is explained. We demonstrate the working principle and
measurements on fused silica and silicon microlenses and benchmark the experimental results with measurement data
obtained with well established micro-optics instrumentation tools.
In this invited paper, we first address the differences between the uses of coherent anti-Stokes Raman scattering (CARS)
as light generating mechanism in Raman devices and as optical analysis tool in spectroscopy. Next, with respect to the
light generating functionality of CARS, we briefly review the latest progress on CARS-based Raman wavelength
converters in silicon-on-insulator (SOI) technology and explain a new approach for boosting the efficiency of these
converters. Finally, we show that the CARS process is also able to extract heat from a Raman-active medium and that
therefore CARS can be used for reducing the heat dissipation in SOI-based Raman lasers.
In this invited paper, we first discuss different submicron- and nanoscale structures that have been introduced over the
past few years to enhance the Raman scattering efficiency in two important materials, namely silicon and hydrogen gas.
Next, we explain how the heat dissipation in silicon- and hydrogen-based Raman lasers and amplifiers could be
intrinsically reduced by the use of coherent anti-Stokes Raman scattering (CARS). We conclude by numerically
demonstrating that with this CARS-based heat mitigation technique the heat generation in these Raman devices could be
suppressed with at least 30%.
Professional societies sponsor student chapters in order to foster scholarship and training in photonics at the college and graduate level, but they are also an excellent resource for disseminating photonics knowledge to pre-college students and teachers. Starting in 2006, we tracked the involvement of SPIE student chapter volunteers in informal pre-college education settings. Chapter students reached 2800, 4900 and 11800 pre-college students respectively from 2006-2008 with some form of informal instruction in optics and photonics. As a case study, the EduKit, a self-contained instruction module featuring refractive and diffractive micro-optics developed by the European Network of Excellence on Micro-Optics (NEMO), was disseminated through student chapters in Argentina, Belgium, Canada, China, Colombia, India, Latvia, Mexico, Peru, Russia, Singapore, South Africa, and the United States. We tracked the movement of this material through the network, up to the student-teacher feedback stage. The student chapter network provided rapid dissemination of the material, translation of the material into the local language, and leveraged existing chapter contacts in schools to provide an audience. We describe the student chapter network and its impact on the development of the EduKit teaching module.
In this invited paper, we will first discuss the recent research progress regarding silicon-on-insulator (SOI) Raman
wavelength converters, the working principle of which is based on the four-wave mixing process of coherent anti-Stokes
Raman scattering (CARS). Next, we will present our research results on other aspects of CARS in SOI waveguides. First,
starting from the basic formalism for CARS we will show that, in contrast to what most scientists believe, CARS exchanges
energy with the Raman medium in which it takes place and is even able to extract energy (i.e. extract phonons) from it.
Furthermore, we will introduce a novel CARS-based approach to reduce the heat dissipation in Raman lasers due to the
quantum defect between pump and lasing photons, and we will numerically demonstrate that with this "CARS-based heat
mitigation technique" the quantum-defect heating in SOI waveguide Raman lasers could be reduced with as much as 35%.
We present different methods to enhance the effectiveness of CARS-based heat mitigation, a novel approach for reducing the quantum-defect heating in Raman lasers. More specifically, we discuss the influence of the CARS-related phase mismatch and of backward Raman scattering on our CARS-based heat mitigation technique and explain how these heat-mitigation-affecting factors should be managed to enhance the effectiveness of our technique. To illustrate the feasibility of obtaining efficient CARS-based heat mitigation, we discuss to what extent the described effectiveness-enhancing methods can be applied to near- and mid-infrared silicon-based Raman lasers. Finally, we numerically demonstrate that for near-infrared silicon-based Raman lasers a heat mitigation efficiency of 15% can be obtained, whereas the corresponding efficiency for their mid-infrared counterparts can be as high as 35%.
We show that the novel heat mitigation technique called "Coherent Anti-Stokes Raman Scattering (CARS)-based heat
mitigation" is able to substantially reduce the quantum-defect heating in hydrogen-based Raman lasers. This CARS-based
heat mitigation technique causes the amount of phonons created in the hydrogen Raman medium to decrease by
establishing an increase of the ratio of the number of anti-Stokes photons to the number of Stokes photons coupled out
of the laser. To illustrate the effectiveness of this heat mitigation approach for a concrete hydrogen-based Raman laser
setup, we numerically demonstrate for a Raman laser based on a hydrogen-filled hollow core photonic crystal fiber that
the heat dissipation can be reduced with at least 30%.
We present a novel approach to intrinsically mitigate the heat dissipated in Raman lasers due to the pump-Stokes
quantum defect. We explain the principle of this so-called "Coherent Anti-Stokes Raman Scattering (CARS)-based heat
mitigation", which is based on decreasing the amount of phonons created in the Raman medium by increasing the ratio
of the number of anti-Stokes photons to the number of Stokes photons coupled out of a Raman laser. To illustrate the
potentialities of this optical cooling technique, we numerically demonstrate that for mid-infrared silicon-based Raman
lasers the heat dissipation can be reduced with at least 35% by the use of CARS-based heat mitigation.
We present the first modeling results for the Stokes and anti-Stokes output of a mid-infrared continuous-wave silicon-based
Raman laser. These emission characteristics are generated by the use of an iterative resonator model, the loss
terms of which we adapted for the case of silicon-based Raman lasers operating in the mid-infrared spectral domain.
These loss terms contain besides linear losses also the three-photon absorption losses that occur in this type of lasers.
We discuss the behavior of this three-photon absorption mechanism and its influence on both the Stokes and anti-Stokes
output. Finally, we compare these emission characteristics with the corresponding simulation results for a near-infrared
silicon-based Raman laser in which linear losses, two-photon absorption losses and free carrier absorption losses occur.
We present a novel numerical model that allows determining the Stokes and anti-Stokes emission characteristics of a
continuous-wave silicon-based Raman laser. This so-called iterative resonator model evaluates for every half roundtrip
time the longitudinal distribution of the intra-cavity pump, Stokes and anti-Stokes fields propagating in forward and
backward directions, while taking into account the two-photon absorption losses and free carrier absorption losses
occurring in the silicon laser medium. Furthermore, we demonstrate that our model exhibits important advantages in
comparison with the power distribution model used for silicon-based Raman lasers. Finally, we present the first
numerical simulation results for a silicon-based Raman laser emitting both Stokes and anti-Stokes photons.
We present a novel numerical model describing the continuous-wave operation of Raman lasers. This so-called
'iterative resonator model' calculates how the forward- and backward-propagating Stokes and anti-Stokes electric fields
inside the Raman laser cavity grow at the expense of the intra-cavity pump fields. We show that the iterative resonator
model exhibits important advantages in comparison with the rate equation model used for e.g. hydrogen-based Raman
lasers.
Power performance of a compact, broadly tunable, continuous-wave (cw) Cr2+:ZnSe laser pumped by a thulium fiber laser at 1800 nm was investigated. In the lasing experiments, a Cr2+:ZnSe sample with a small-signal differential absorption coefficient of 11 cm-1 and a fluorescence lifetime of 4.6 μs was used. An astigmatically compensated x-cavity with 15 % output coupler produced as high as 640 mW of output power at 2480 nm with 2.5 W of incident pump power. Resonator losses were investigated using three different methods, and an in-depth analysis of the results was performed. The stimulated emission cross section values determined from laser threshold data and fluorescence measurements were in good agreement with each other. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster-cut MgF2 prism and a single set of optics.
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