We report frequency combs formation in THz QCL ring cavities. The double metal waveguide laser is encapsulated in benzocyclobutene (BCB) on which the top contact is deposited. This allows to explore alternative designs such as ultrathin ring cavities and coupled double ring waveguides avoiding issues with the electrical connection of the. Ring laser operating in dense comb regime with spectral bandwidth of ~500 GHz is here reported. In addition to the frequency comb operation sech2-shaped spectra are observed in RF-injected ring lasers and dispersion compensated double ring cavities, hinting at the existence of soliton regimes in the QCL.

Non-linear properties of buried heterostructure ring quantum cascade lasers have been investigated. Clear symmetry breaking between two counter-propagating modes has been observed with a transition to a emission that has a solitonic characteristics.

A plethora of applications have recently motivated extensive efforts on the generation of low noise Kerr solitons and coherent frequency combs in various platforms ranging from fiber to whispering gallery and integrated microscale resonators. However, the Kerr (cubic) nonlinearity is inherently weak, and in contrast, strong quadratic nonlinearity in optical resonators is expected to provide an alternative means for soliton formation with promising potential. In this talk we overview recent experimental results on formation of two types of dissipative quadratic solitons in optical parametric oscillators, namely temporal simultons in the mid-infrared and temporal walk-off induced solitons. Unlike Kerr solitons, these quadratic solitons occur in low-finesse resonators and can provide substantial pulse compression and high conversion efficiencies. We present a route to significantly improve the performance of these demonstrated quadratic solitons when extended to an integrated platform.

Frequency combs are coherent light sources comprising multiple evenly spaced emission lines, allowing coherent sampling over a broad part of the optical spectrum. The addition of a second frequency comb results in a dual comb. Now, one comb can be used as a local oscillator frequency reference for the other, allowing spectroscopic measurement to take place at radio-frequencies. An important figure of merit is the relative frequency stability of the two combs. In this work we demonstrate efficient generation of ultrastable dual combs using an electro-optic whispering gallery mode resonator, with a relative comb line stability of order 1 mHz.

Raman lasers are a valuable resource for frequency conversion of coherent light. Their drawback of requiring high pump powers could be mitigated by nanophotonic engineering. The implementation of a low-threshold Raman laser in the visible, however, has remained elusive due to material and fabrication limitations. In this work, we report a novel platform consisting of a diamond membrane embedded in an open-access Fabry-Perot microcavity. Based on the large quality factors of our device, we predict that a sub-mW lasing threshold for visible wavelengths is within reach by harnessing a doubly resonant configuration. We demonstrate a >THz continuous tuning range of doubly-resonant Raman scattering by exploiting the in situ tuning capability of our platform. Our results pave the way for the creation of a universal low-power frequency shifter.

We report for the first time the generation of a two-octave spanning supercontinuum (SC) from 700 nm to 2800 nm in a 20 cm non-silica graded-index multimode fiber. We study the SC generation and associated nonlinear instabilities in different dispersion regimes and characterize the SC stability. Significantly, under particular injection conditions, we observe clear signatures of self-cleaning dynamics with a near single-mode spatial intensity distribution at the fiber output. Our results are confirmed by numerical simulations of the 3D+1 generalized nonlinear Schrodinger equation

We design and fabricate a stable cavity for a highly multimode semiconductor laser. After suppressing the lasing instabilities, we utilize the spatio-temporal interference of numerous lasing modes to create ultrafast random intensity fluctuation in space and time. By spatial multiplexing of the laser emission, we produce 127 statistically independent parallel bit streams from a chip-scale laser. The total bit rate reaches 250 Terabit/s, two orders-of-magnitude faster than the state-of-the-art. The unpredictability and non-reproducibility of random bits are guaranteed by spontaneous emission noise originating from quantum fluctuations. Our scheme is robust, compact, and energy-efficient with applications in cybersecurity and stochastic modeling.

We present a one dimensional photonic crystal, made of Gallium-Phosphide, as an optomechanical oscillator with low phase noise. The heterogenous integration on Silicon-on-Insulator circuitry allows the evanescently coupling of light at telecom wavelengths from the silicon waveguides into the photonic wire crystal. Thanks to the strong interaction between the optical field and mechanical field, the mechanical oscillation at 3.35 GHz is directly imprinted on the optical carrier. An external opto-electronic feedback loop with time-delay is constructed to further stabilize the oscillation. We achieved a phase noise of -111dBc/Hz at 100 kHz offset frequency with sub-Hz linewidth of 0.67 Hz.

Studying molecules and nanoparticles one at a time provides valuable information about their chemistry and physics, including temporal dynamics and heterogeneity. Our group developed a technique using microresonators as ultrasensitive thermometers, with which we study single nanoparticles using photothermal absorption spectroscopy. I will present recent progress in which we applied this technique to study and control the chemical dynamics of single gold nanorods under aqueous conditions. This advancement adds both to the toolkit of single particle techniques and the versatility of microresonator technology. I will also describe outstanding challenges and recent progress in adapting this technique for more sensitive experiments.

This Conference Presentation, “In Memoriam Alan Paxton,” was recorded at SPIE Photonics West held in San Francisco, California, United States.

Optical vortex possesses a ring-shaped spatial form and an orbital angular momentum, associated with its helical wavefront. In this presentation, we review the direct generation of optical vortex modes from solid-state lasers and the nonlinear wavelength extension of optical vortex modes. We also address exotic sharing of the orbital angular momentum among the generated optical vortex beams involved in the nonlinear process. Furthermore, we present diode-pumped orbital Poincaré Pr3+:LiYF4 lasers, enabling selective generation of all eigen-modes mapped on the equivalent orbital Poincaré sphere.

We will provide a brief overview to Structured Light – in particular to structured polarisation profiles, with specific attention to vector vortex modes, which possess inhomogeneous polarisation profiles. In this work, we create polarisation structures that not only rotate about their propagation axis, but can be controlled to accelerate independently from their spatial profile. This we achieve with weighted superpositions of oppositely charged scalar Bessel beams encoded with a Digital Micromirror Device (DMD). We also investigate their angular accelerating Stokes vectors and intensity transport between local positions within the field. Lastly, we present a digital analogy to Stokes polarimetry in order to extract the polarisation structure of such fields from only four measurements as opposed to the usual six measurements. Instead of using static polarisation optics, we use a Polarization Grating (PG) to project a mode into left- and right-circular states which are subsequently directed to a DMD to impart a phase retardance for full polarisation reconstruction.

We generate a large coherent laser array imbued with topological charge by addressing the phase retrieval problem to reconstruct the desired phase distribution from its corresponding Fourier intensity pattern. By employing the many modes in a degenerate laser cavity as a parallelised solver and by limiting its finite domain to lift the degeneracy between the competing phase distributions, an optimum solution with tailored multi-singularities is found. We implement the required constraints within the cavity using binary amplitude masks as opposed to sophisticated phase devices, paving the way as a simple technique to generate large structured vortex arrays at the source.

Bessel beams are important for light-sheet microscopy, optical trapping, nonlinear optics, or laser materials processing. For these applications, it could be very attractive to control polarization along propagation. We demonstrate, for the first time, polarization shaping of an optical pulse along its propagation. We use laser-induced nanogratings to create a polarization-shaping element, which controls the polarization distribution of a diffraction-free Bessel beam. We successfully generated femtosecond Bessel beams with a length exceeding 60 µm for a submicron focal spot diameter, where the axis of the linear polarization continuously rotates from zero up to 180 degrees.

Bessel beams are quasi-nondiffracting beams. They find numerous applications in high-aspect ratio laser material processing, optical trapping and nonlinear photonics. It is desirable to reach the highest angles to increase the local intensity and reduce the diameter of the laser-generated nanostructures. Here we report on experimental and numerical results of a new Bessel beam shaper which reaches half-cone angle of 48 degrees, i.e. approximately twice higher than state of the art. Numerical analysis of the setup and impact of component misalignment will be presented.

The constant increase of peak energy on high-intensity lasers necessitates the combined control of the laser pulse (with pulse shapers for temporal characterization) and the wavefront (with deformable mirrors for spatial characterization). Focusing the beam on the target creates space time couplings that were typically neglected until now. We have developed a solution that provides direct, spectrally-resolved wavefront measurements to characterize and quickly diminish those couplings. We will present concrete results on beamlines, highlighting the interest of a high spectral and spatial resolution system. Its simplicity of use will be demonstrated using the quick alignment of compressor gratings as an example.

Transmissive holographic phase masks – i.e., complex phase-structures embedded into the volume of transmissive Bragg gratings – have been shown to possess a high degree of achromatism, uniquely suited for applications utilizing broadband optical-sources. Here we report on the holographic construction of their reflective counterpart in photo-thermo-refractive glass, operating as tunable narrowband spectral filters that simultaneously provide phase incursion for spatial beam-transformation. Such an element is further employed in a linear, wavelength-tunable, continuous-wave Yb3+:KYW laser for intracavity beam-shaping.

Optical metasurfaces enable the most general spin-orbital momentum transformations that map the higher order Poincaré sphere. I will first review our work on metasurfaces spin-to-orbital momentum converters that allow beam control and structuring. I will then introduce our latest results in the creation of coupled lasers with design OAM and topology.

Broad area diode lasers can effectively scale power, but suffer from degraded beam quality largely due to filamentation in a Fabry- Pérot cavity. Angled cavity waveguide has been proven to be able to suppress filamentation, but some high order modes still exist in the mid-IR angled cavity diode lasers we have fabricated recently. We discovered that removing certain regions that don’t contribute gain to the fundamental mode will shift mode competition toward the fundamental mode. Laser devices with such a modified angled cavity waveguide exhibit improved beam quality, and demonstrate a ~2 fold brightness enhancement to their Fabry-Pérot counterparts.

Recently, with the development of fabrication technology, sub-nm patterning has been developed, and it has become sufficiently possible to make a nanostructure having a sub-wavelength period. For this reason, metasurface has been a topic of increasing interest in the field of nanophotonics. In this paper, we report the results of realizing mode locking by inserting a metasurface in the form of a saturable absorber into an Yb-doped fiber laser. The metasurface-based saturable absorber has the advantage of reducing the loss due to the deterioration of the existing saturable absorber.