We study a semiconductor laser coupled to two mirrors at a distance. Understanding such a delayed feedback system and how it can make the laser behave chaotically could lead to better random number generators, safer communications, and more widespread use of these devices. Based on previous reports, the two delays are positioned in the long cavity regime and differ in the order of half the relaxation oscillation period (ROP) to limit the appearance of the so-called time-delay signature (TDS). We show theoretically that a change of the feedback phase has a crucial impact on the TDS and chaos bandwidth (CBW). At intermediate values, a change in the feedback phase will either suppress or enhance the TDS. For high feedback rates, where the chaotic bandwidth is much higher, the system can switch rapidly between stable and chaotic states due to small variations of the feedback phase. We show experimentally that the CBW is increased by increasing the feedback strength if the feedback phase is controlled. In summary, with two feedback loops, one can further suppress the TDS and increase the CBW, given that the feedback phases can be controlled accurately. Our results contrast with the one-delay system, for which the feedback phase has only limited impact if the feedback mirror is far from the laser.

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.

This study experimentally investigates the synchronization of chaos produced by semiconductor lasers in a cascade injection configuration. A tunable master laser induces chaos through optical injection into a transmitter laser, which subsequently injects light into a receiver laser. Synchronization between the transmitter and receiver lasers is achieved with a correlation coefficient of 90% over a measurement bandwidth of 35 GHz. Two distinct parameter regions exhibiting robust synchronization are identified, characterized by alignment of the receiver laser’s oscillation frequency with either the transmitter laser or the master laser frequency. Additionally, our experimental setup allows for the generation of two distinct chaos regimes, with correlation coefficients exceeding 90% for each.

A Delay Differential equation model of a bidirectionally coupled two section comb source is investigated. The model consists of a single mode Primary Laser (PL) bidirectionally coupled to a single mode Secondary Laser (SL). Optical Frequency Combs (OFCs) are then generated in the SL via gain switching. An investigation into the impact of this gain switching frequency on the comb generated in each laser is then performed. Stable, well defined combs are obtained for modulation frequencies close to the Relaxation Oscillation Frequency (ROF) of the SL whilst poorly-defined, likely chaotic combs are produced when gain switching close to the ROF of the PL.

The study focuses on stabilizing subharmonic nonlinear dynamics in semiconductor lasers for optical frequency comb (OFC) generation. The proposed system consists of two cascaded optical injection stages. By injecting the first stage with proper power and frequency, period-one (P1) dynamics are invoked, then leading P1 dynamic injection into the second stage. With adjusted power in the second stage, undamped relaxation oscillations trigger subharmonic nonlinear dynamics. This achieves OFC generation with subharmonic oscillation sidebands, generating over 15 comb lines, and a bandwidth greater than 140 GHz. We have also proposed a cascaded injection-locking scheme to improve microwave comb signal quality limited by laser-induced instability.

We consider two issues concerning the dynamics of nanolasers: the impact of their large noise on the deterministic trajectories and the interpretation of the statistical results coming from the photon statistics. The second issue, due to the lack of sufficiently sensitive and fast detectors, represents an unavoidable bottleneck in the analysis of any dynamics and is discussed in detail. Our study reveals several important results. Statistics and dynamics provide complementary information, but the former is not able to reliably distinguish different dynamical regimes. Inferring a coherence emission regime, or degree of coherence, from autocorrelation functions is fraught with interpretative traps. Finally, we address the challenge posed by external noise, which dramatically distorts the statistical information derived from the autocorrelations. We introduce an empirical indicator capable of identifying the lowest pump value from which autocorrelation values become reliable, based on a single sequence of noisy data that can be applied to the same-time, second-order autocorrelation function. This indicator is a valuable tool for experimentalists.

We compare a novel quantum mechanical model of lasers, which includes all two-particle correlations, with the Coherent-Incoherent Model (CIM), where truncation eliminates these effects. Numerical results for the simple case of identical single-electron quantum dots are presented for two cases: only the laser mode is coupled to the quantum dots; the coupling is extended to non-resonant modes. We find coexistence between non-lasing and lasing states, together with a minimum number of photons required to initiate the laser action. The correlations introduce a non-zero variance in the field, which is otherwise strictly zero in the absence of interparticle correlations.

GeSn alloys hold the promise for the development of on-chip, scalable, industry-compatible light sources. Here, we introduce a novel strain engineering approach to create tensile-strained GeSn microlasers. Through a unique lithographic design, the initially harmful compressive strain intrinsic to the GeSn layers is converted to the beneficial tensile strain and amplified on the GeSn microbridges. By tuning the design parameters of the microbridges, multiple lasers with different tensile strains were achieved on a single chip. We anticipate that increasing the tensile strain will lead to a shift in the lasing wavelength and an improvement in the laser threshold. This work presents a straightforward and cost-effective solution for developing diverse on-chip laser arrays, enabling applications such as on-chip wavelength division multiplexing.

The compactization of lasers is an ongoing challenge in increasing their effectiveness and integrability of other systems, from nanosatellites to medical devices. The need to decrease their dimensions, especially, for diode-pumped solid-state microchip laser systems causes significant problems with beam quality. Such lasers feature an additional problem of Brightness to output power scaling power. We report an approach where we used a thin film dielectric Fano-like resonance structure as a replacement to a conventional output coupler to overcome this challenge. The structure is engineered to function as a flat spatial filter element for selecting the fundamental transverse mode of the cavity. We achieved an increase of 2x over a conventional setup in CW operation. The data matches well with the numerical analysis performed for a single longitudinal mode model. We predict that this discovery could lead to advanced power scaling in submillimeter cavities, while maintaining the beam quality.

In this report, we experimentally analyze the effect of optical injection of a signal with a single-sideband (SSB) modulation on a multi-wavelength laser (MWL) integrated on a photonic integrated circuit. The optical injection of an SSB modulation into the MWL leads to spectral multiplication of the signal around the un-injected modes of the MWL. This multiplication arises from the modulation of the carrier density inside the cavity and the strong nonlinear coupling between different modes of the MWL. We report an asymmetric power evolution of the generated sidebands around the injected and un-injected modes of the MWL while the modulation frequency is swept. The power and modulation bandwidth of the signal emerging around the injected and un-injected modes strongly depend on the position of the cavity resonance frequency of the injected mode, which can be tailored by adjusting the injection strength and the detuning of the injected signal.

Heterogeneous integration of III-V semiconductor material on a Silicon substrate presented a promising solution to the challenge of laser integration in Silicon photonics. This will greatly benefit sensitive applications such as Analog Radio over Fiber (ARoF) in achieving a low-cost, highly integrated, and limited noise architecture. Meanwhile, careful laser design and characterization are essential to allow for high power emission, wide tunable operation, and the reduction of Relative Intensity Noise (RIN) which are vital to the performance of the ARoF through enhancing the signal-to-noise ratio and dynamic range. This paper presents two designs of a ring-resonator-based widely tunable laser, all designed by the III-V Lab and fabricated at the CEA-Leti, with differences in their vernier filter and Sagnac mirrors configuration. These laser chips have been characterized and compared through their output power, wavelength tunability evaluation, and RIN under different bias conditions. The presented results show a threshold current≤40 mA, a large wavelength tunable range of up to 48 nm, and a low RIN of up to −150 dB/Hz

Leading-edge machine learning algorithms require large amounts of matrix multiplications, which absorb significant computational resources in modern digital electronic systems. Analogue optical computing systems consisting of light sources, modulators and receivers may perform these operations with much higher efficiency. We introduce an integrated device based on electro-optically modulated (EOM) vertical-cavity surface-emitting lasers (VCSELs) that can perform analog multiplication at >28 GHz and at <20 mW power consumption. Due to its monolithic integration, the EOM VCSEL may be used as a building block for integrated optical computing devices. Development of such devices can help create 3-dimensionally integrated computing and communication systems.

We present a study of high-power quantum-cascade lasers (QCL) for 8 μm spectral range with active regions of latticematched to InP substrate and strain-balanced designs. The use of the strained quantum well/barrier pairs made it possible to increase the energy barrier between the upper laser level and continuum by ~ 200 meV. Our experiments show that utilization of the strain-balanced design of the active region makes it possible to more than double the characteristic temperature T₀ to 253 K from 125 K for the lattice-matched design. In pulsed mode, QCLs with strain-balanced active region demonstrated high efficiency of 12% and high output optical power of 21 W (over 10 W per facet). This is the highest value of the optical power demonstrated to date in 8 μm spectral region to the best of our knowledge.

Often described as the quantum mechanical counterpart to the classical random walk, the quantum walk is characterized by a ballistic spread of the spatial particle probability distribution, with fundamental implications as well as practical relevance, e.g., for quantum algorithms. Recently, it has been shown that optical frequency combs can mimic the behavior of a quantum walk. This “quantum walk comb” is induced by the injection of a radio frequency (RF) signal into a ring-shaped, mid-infrared quantum cascade laser (QCL). Here, we report on a compact and accurate extension to the Maxwell-Bloch formalism to model RF injection into ring QCLs, including the dependence of the electronic system Hamiltonian on the RF bias field which co-propagates with the optical waveform. We present dynamical simulations of the quantum walk comb in good agreement with experiment, reproducing key features such as the ballistic buildup of the comb and the resulting Bessel-like spectra.

We present a study of quantum cascade laser dynamical properties accounting for the Joule heating released in the active region. In particular, we study the QCL emitting at 8 μm in the pulsed pumping mode and present experimental measurements, as well as a theoretical description of the QCL build-up time, showing the features appearing due to the Joule heating released inside the active region.

Semiconductor lasers have become the light source of choice in many applications. For example, IR VCSELs are widely used for sensing purposes in consumer electronics, replacing the LEDs. Advantages in manufacturing and the ability to tailor the properties to the requirement of different applications were the key success. On the other hand, longer wavelength i.e. SWIR (Short-wave Infrared) are appearing and expected to rise further since they create new possibilities and applications. Eventually, detailed and accurate electrical and optical characteristics of these illumination sources is essential. LIV curves and spectrum analysis are fundamental measurement to determine the operating characteristics. They are widely used at various stages since it is critical to identify failed DUTs early in the manufacturing process. In this study, we introduce complete measurement setup for LIV with spectrum analysis of SWIR semiconductor lasers. These lasers have wavelength longer than 1000nm and therefor GaAs or silicon based sensors are not applicable. Hereby InGaAs sensors with appropriate optics and electronics are combined. Our measurement set up benefits from a highresolution array spectroradiometer, highly reflective integrating sphere and sensitive photodiode sensor. Further, the measurement setup is metrologically calibrated and is traceable to the international standards. Consequently, the LIV curves and spectrum of the DUT were measured at high spectral and electrical resolution. From LIV curves power conversion efficiency, threshold current, slope efficiency, kinks and rollover point were further calculated and analyzed. At the same time, the DUT temperature was controlled and tempered at different temperatures. The influence of the temperature on the laser performance, characteristics and properties is thoroughly analyzed. Extension and further atomization of our measurement routine is required to facilitate the semiconductor lasers development and as well to speed up the industrialization of the semiconductor lasers.

Low-loss coupling of VCSELs (vertical-cavity surface-emitting lasers) to optical fibres is a key issue for increasing their use in optical communications and instrumentation systems. However, tolerances on angular tilts and lateral misalignments are tight, particularly in the case of single mode devices. To address this challenge, a new fabrication method based on near-infrared single-mode self-writing (NIR-SM-SWW) of a polymer waveguide was developed and tested for the coupling of two single mode fibers at 850 nm (Thorlabs 780-HP) with a mode field diameter close to that of 850 nm single mode VCSEL. The specificity of our method is to use a writing wavelength identical to that designed for single mode propagation in the fibers, leading to a single step photopolymerization process that will be directly transferable to 850 nm VCSEL-to-fiber coupling. First results show coupling losses at 850 nm as low as 0.86 dB for a distance between the fibers of 100 μm.

We demonstrate two highly coherent tunable high power laser concepts, based on a III-V semiconductor VECSEL technology, operating in the 1μm wavelength range. We report experimentally and theoretically the existence of deterministic dynamics of a coherent semiconductor laser field, with a route to robust single-frequency operation exhibiting broad nonlinear frequency pulling far above the thermally-assisted conventional tuning range. Thanks to a complementary design, we demonstrate an inhibited laser state exhibiting high power, high spatial and temporal coherence under ultralow light matter interaction, overcoming fundamental and technical limitations of common on the shelf laser technology, like quantum, electronic and thermal noise, as well as thermal lensing induced wave aberration.

Spot size is an important parameter of the laser, which not only represents the resolution of laser, but is also involved in the calculation of other parameters. Nowadays, CCD imaging systems, scanning imaging systems, and other sensors are used to measure the laser spot size. But they are all lacking flexibility when measuring the spot size in different locations, not to mention their high cost. In this study, a new spot size measurement device based on laser back-injection interferometry was presented. The photodiode integrated with the laser diode was used to collect the feedback laser, then the laser spot size was calculated by the feedback current. A commercial CCD imaging system was used to provide the laser spot size as a reference. Results show that our spot size measurement device could measure the spot size (Full Width Half Maximum) of 5 laser diode modules both in the x (Gaussian-like profile) and y (top-hat-like profile) direction through scanning-slit. Though there are variations between the scanning-slit results and spot sizes from the CCD imaging system due to the diffuse and specular reflection, the accuracy of the spot size measurement device ranges from 96.07 % to 99.46 %, which proves the reliability of our device. It is believed that our device could provide an alternate method for laser spot size measurement, which is cost-effective, easy to operate, and accurate.

This study investigates the influence of controlled mechanical strain on the wavelength characteristics of Vertical- Cavity Surface-Emitting Lasers (VCSELs), crucial components in optoelectronics, particularly in data centers. Using a custom four-point bending module, we systematically analyze the impact of strain on VCSELs by examining the wavelength evolution under varying strain levels. we report a consistent blue shift in the laser’s wavelength with increasing strain while maintaining stable power output. These findings highlight the potential of strain manipulation as a reliable technique for wavelength tuning in VCSELs, offering prospects for enhancing their performance in optical communication applications.

Exposing semiconductor lasers to external optical feedback can significantly affect their emission properties by, e.g., generating complex dynamics or enabling coherence control. When considering semiconductor multi-wavelength lasers, i.e., lasers designed to emit at two or more distinct wavelengths, feedback has been used to demonstrate emission switching between the different wavelengths. In particular, by controlling the phase shift in the feedback cavity, fast (nanosecond timescale) wavelength switching between two, three and even four of the lasing modes, separated by more than a THz, has been observed experimentally.

The wavelength control is not straightforward since the response of the laser depends on various parameters such as the differential gain between the modes or the cross-saturation parameters (or carrier population gratings). Based on a model relying on a multi-mode extension of Lang-Kobayashi rate equations, we explore the parameter space in terms of feedback strength, delay and modal phases, to identify regions suitable for wavelength switching. In this direction, we determine a feedback strength threshold and detect the appearance of dynamics with longer delays.

Chaotic dynamics in semiconductor lasers under feedback is useful for ranging, security, reinforcement learning, and random bit generation. Complementing temporal characterizations, geometric characterization is realized using the correlation dimension D2. Numerically, a coherent combination of injection and feedback on a laser is considered in showing dimensional enhancement that qualitatively agrees with recent experiments. Experimentally, measurements of the dimensions continue to show enhancement in complexity by coherently incorporating injection and feedback without fixing the phase. The measurements are enabled by employing a large data size, while re-embedding through including a principal component analysis (PCA) is considered. Also, balanced homodyning with a delay is considered on a laser under injection alone, where the estimated dimension is found to nearly double as the baseband is strengthened. Based on single-mode laser dynamics, the coherent approaches of continuous-wave injection, delayed feedback, and balanced homodyning are demonstrated for manipulating the chaotic complexity for applications.

We show that a III-V semiconductor vertical external-cavity surface-emitting laser (VECSEL) can be engineered to generate light with a customizable spatiotemporal structure. Temporal control is achieved through the emission of temporal localized structures (TLSs), a particular mode-locking regime that allows individual addressing of the pulses traveling back and forth in the cavity. The spatial profile control relies on a degenerate external cavity, and it is implemented due to an absorptive mask deposited onto the gain mirror that limits the positive net gain within two circular spots in the transverse section of the VECSEL. We show that each spot emits spatially uncorrelated TLSs. Hence, the spatiotemporal structure of the light emitted can be shaped by individually addressing the pulses emitted by each spot. Because the maximum number of pulses circulating in the cavity and the number of positive net-gain spots in the VECSEL can be increased straightforwardly, this result is a proof of concept of a laser platform capable of handling light states of scalable complexity. We discuss applications to three-dimensional all-optical buffers and to multiplexing of frequency combs that share the same laser cavity.

A single-mode external cavity diode laser (ECDL) emitting in the blue spectral region is developed. The ECDL, which uses a low-power Fabry-Perot laser diode, is designed in the Littrow configuration using a reflective holographic grating. The ECDL has a narrowband emission at 448 nm of 0.01 nm that coincides with a strong absorption cross-section of NO₂ gas molecule, tuning ranges of 4.0 nm just above the threshold and 0.2 nm at high injection current. A maximum output power of 60 mW and an efficiency of 80 % with respect to the Fabry-Perot laser diode in free-running condition are achieved. High stability of the laser system over many hours was also achieved with a fluctuation of less than 1 %.

Low-noise lasers are critical in precision spectroscopy, displacement measurements, and optical atomic clock development. These fields require lasers with minimal frequency noise, combining cost-effectiveness with robust design. We introduce a simple, single-frequency laser that uses a ring fiber cavity for self-injection locking in a standard semiconductor distributed feedback (DFB) laser. Our design, unique in its use of polarization-maintaining (PM) singlemode optical fiber components, offers a maintenance-free operation and enhanced stability against environmental noise. Achieving continuous wave (CW) single-frequency operation, it maintains this state with low-bandwidth active optoelectronic feedback. The laser operates at ~8 mW, reducing the Lorentzian linewidth to ~75 Hz and achieving phase and intensity noise levels below –120 dBc/Hz and –140 dBc/Hz, respectively. Additionally, its thermal stabilization limits frequency drift to < 0.5 MHz/min with a maximum deviation of < 8 MHz. Implementing this design in integrated photonics could significantly cut costs and space requirements in high-capacity fiber networks, data centers, atomic clocks, and microwave photonics.

We develop a high-precision chaos lidar system using broadband optical chaos from a semiconductor laser subjected to optical feedback. We study how the detector bandwidths, cut-off frequencies, signal-to-noise ratios, and peak sidelobe levels in correlation affect the precision in ranging. With a detector bandwidth of 1600 MHz, a precision of 0.43 mm is achieved from the chaos-modulated pulses with a pulse width of 70 ns. The demonstration and comparison of 3D imaging obtained by waveforms with bandwidths of 1600 and 400 MHz show an enhancement in image quality with broader bandwidths and higher cut-off frequencies.

The pivotal role played by semiconductor lasers in telecommunications and data storage applications requires dealing with time lag and relaxation oscillations, which limit bandwidth and reliability. As an alternative to the mitigation measures traditionally employed, we analyze the potential of size downscaling and investigate the intrinsic physical features of lasers down to the nanoscale. An analysis of the dynamical properties as a function of scale, with standard models, highlights the intrinsic potential of nanolasers as advantageous sources of light for information. Noise response and characteristic times strongly confirm that considerable gain can be obtained from small devices, thus encouraging efforts directed at solving technological hurdles.