High power widely tunable frequency-doubled 490 nm blue semiconductor disk laser.

This paper presents a high power widely tunable frequency-doubled semiconductor disk laser emitting at 490 nm wavelength. The laser utilizes a specially designed gain chip with widened gain spectrum at the center wavelength of 980 nm, along with an anti-resonant microcavity, to extend the tuning range of the wavelength. A type-I phase-matched 5 mm length LBO crystal is used as the nonlinear crystal, and a fused quartz birefringent filter (BRF) is introduced to polarize the fundamental emission and narrow the linewidth of the laser.

Over 10 kW peak-power low repetition rate passively mode-locked VECSEL using a saturable Bragg reflector.

Reducing the repetition rate is one of the effective ways to increase the peak-power of the mode-locked pulses. However, for a vertical-external-cavity surface-emitting laser (VECSEL), the carrier lifetime in the nanosecond regime limits the further reduction of the pulse repetition rate, or in other words, limits the average output power of the mode-locked laser at low repetition rates, and ultimately restricts the peak-power of the pulses. This work uses a specially designed saturable Bragg reflector to start the mode-locking, and both low repetition rate and high average power are achieved simultaneously in a passively mode-locked VECSEL.

Frequency tripled semiconductor disk laser with over 0.5 W ultraviolet output power.

Semiconductor disk lasers can produce high output power and good beam quality simultaneously. The high intracavity circulating power of about hundreds of watts, along with the flexibility of tailorable emitting wavelengths, make it an attractive light source for obtaining ultraviolet (UV) radiation from near-infrared lasers through nonlinear frequency conversion. This work reports a frequency tripled 327 nm semiconductor disk laser with record output power and wavelength tuning range by using a type-I phase-matched LiBO (LBO) crystal and a type-I phase-matched β-BaBO (BBO) crystal as the frequency-doubling and -tripling crystals respectively.

Continuous-wave operation of 1550 nm low-threshold triple-lattice photonic-crystal surface-emitting lasers.

Benefitting from narrow beam divergence, photonic crystal surface-emitting lasers are expected to play an essential role in the ever-growing fields of optical communication and light detection and ranging. Lasers operating with 1.55 μm wavelengths have attracted particular attention due to their minimum fiber loss and high eye-safe threshold.

Boosting Perovskite Photodetector Performance in NIR Using Plasmonic Bowtie Nanoantenna Arrays.

Triple-cation mixed metal halide perovskites are important optoelectronic materials due to their high photon to electron conversion efficiency, low exciton binding energy, and good thermal stability. However, the perovskites have low photon to electron conversion efficiency in near-infrared (NIR) due to their weak intrinsic absorption at longer wavelength, especially near the band edge and over the bandgap wavelength. A plasmonic functionalized perovskite photodetector (PD) is designed and fabricated in this study, in which the perovskite ((Cs FA MA )Pb(I Br ) ) active materials are spin-coated on the surface of Au bowtie nanoantenna (BNA) arrays substrate.

Beam waist shrinkage of high-power broad-area diode lasers by mode tailoring.

A new approach was proposed and its role in improvement of the beam quality of high-power broad-area diode lasers was demonstrated, in which a composite arrow array and trench microstructure was used to suppress the beam waist and tailor the high order lateral modes. The beam waist shows a special shrinkage with increasing injection current resulting from the combined effect of mode tailoring and the thermal lens effect. A 58% improvement in lateral beam parameter product was realized compared with conventional broad-area diode lasers.

High power femtosecond semiconductor lasers based on saw-toothed master-oscillator power-amplifier system with compressed ASE.

High power femtosecond semiconductor laser based on saw-toothed taper mode-locked laser and amplifier was demonstrated with compressed amplified spontaneous emission (ASE). The external-cavity mode-locked taper laser generated the clean optical pulses without any sub-pulse components. A semiconductor optical amplifier (SOA) with tilted taper waveguide and saw-toothed edge reduced evidently the ASE background.

Extracting more light for vertical emission: high power continuous wave operation of 1.3-μm quantum-dot photonic-crystal surface-emitting laser based on a flat band.

For long distance optical interconnects, 1.3-μm surface-emitting lasers are key devices. However, the low output power of several milliwatts limits their application.

Loss tailoring of high-power broad-area diode lasers.

Broad-area diode lasers (BALs) with high power are highly desirable for a variety of applications. However, such lasers suffer from strongly deteriorated beam quality due to multimode behavior in the lateral direction. In this Letter, we present an approach to flexibly tailor the optical loss of different-order lateral modes by etching micro-holes on the laser mesa with controlled position and numbers.

Enhancing Third- and Fifth-Order Nonlinearity via Tunneling in Multiple Quantum Dots.

The nonlinearity of semiconductor quantum dots under the condition of low light levels has many important applications. In this study, linear absorption, self-Kerr nonlinearity, fifth-order nonlinearity and cross-Kerr nonlinearity of multiple quantum dots, which are coupled by multiple tunneling, are investigated by using the probability amplitude method. It is found that the linear and nonlinear properties of multiple quantum dots can be modified by the tunneling intensity and energy splitting of the system.

Parity-time symmetry in coherent asymmetric double quantum wells.

A coherently prepared asymmetric double semiconductor quantum well (QW) is proposed to realize parity-time (PT) symmetry. By appropriately tuning the laser fields and the pertinent QW parameters, PT-symmetric optical potentials are obtained by three different methods. Such a coherent QW system is reconfigurable and controllable, and it can generate new approaches of theoretically and experimentally studying PT-symmetric phenomena.

Asymmetric light diffraction of two-dimensional electromagnetically induced grating with PT symmetry in asymmetric double quantum wells.

An asymmetric double semiconductor quantum well is proposed to realize two-dimensional parity-time (PT) symmetry and an electromagnetically induced grating. In such a nontrivial grating with PT symmetry, the incident probe photons can be diffracted to selected angles depending on the spatial relationship of the real and imaginary parts of the refractive index. Such results are due to the interference mechanism between the amplitude and phase of the grating and can be manipulated by the probe detuning, modulation amplitudes of the standing wave fields, and interaction length of the medium.

Near-diffraction-limited Bragg reflection waveguide lasers.

We report a near-diffraction-limited tapered Bragg reflection waveguide laser (BRL) with a 10 μm ridge width, which is significantly larger than the conventional design. The large mode expansion in the vertical waveguide enables a scalable increase in the ridge width for single lateral mode operation. The role of the taper angle in the performance of tapered BRLs with the intrinsic characteristics of a thick vertical waveguide was investigated.

Dynamically tunable multi-lobe laser generation via multifocal curved beam.

Beams with curved properties, represented by Airy beam, have already shown potential applications in various fields. Here we propose a simple method to achieve a multifocal curved beam (MCB). The scheme is based on the ability of microspheres to control the distribution of the light field.

High-brightness diode lasers obtained via off-axis spectral beam combining with selective feedback.

We proposed a modified off-axis spectral beam combining method, based on the concept of selective feedback. A high reflectivity mirror with a fixed width was used to select and couple back the optical modes in the external cavity. The emission power exceeding 20 W with M factors of 2.

Going beyond the beam quality limit of spectral beam combining of diode lasers in a V-shaped external cavity.

A novel spectral beam combining (SBC) approach based on off-axis feedback in a V-shaped external cavity (VSBC) was proposed and demonstrated. A highly reflecting mirror was used to supply the optical feedback by partial overlapping the beam. The advantages of simple setup, output coupler free, tunable beam quality and emission power over traditional SBC were presented.

Investigation of regime switching from mode locking to Q-switching in a 2 µm InGaSb/AlGaAsSb quantum well laser.

A two-section InGaSb/AlGaAsSb single quantum well (SQW) laser emitting at 2 μm is presented. By varying the absorber bias voltage with a fixed gain current at 130 mA, passive mode locking at ~18.40 GHz, Q-switched mode locking, and passive Q-switching are observed in this laser.

Fabrication of TiC-TiB₂/Al Composites for Application as a Heat Sink.

Metal matrix composites reinforced with ceramic particles have become the most attractive material in the research and development of new materials for thermal management applications. In this work, 40-60 vol. % TiC-TiB₂/Al composites were successfully fabricated by the method of combustion synthesis and hot press consolidation in an Al-Ti-B₄C system.

High-power dual-wavelength lasing in bimodal-sized InGaAs/GaAs quantum dots.

In this paper, we demonstrate high power, dual-wavelength (dual-λ) lasing stemming from bimodal-sized InGaAs/GaAs quantum dots (QDs). The device exhibits simultaneous dual-λ lasing at 1015.2 nm and 1023.

Design considerations of high-performance InGaAs/InP single-photon avalanche diodes for quantum key distribution.

InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in practical applications requiring near-infrared photon counting such as quantum key distribution (QKD). Photon detection efficiency and dark count rate are the intrinsic parameters of InGaAs/InP SPADs, due to the fact that their performances cannot be improved using different quenching electronics given the same operation conditions. After modeling these parameters and developing a simulation platform for InGaAs/InP SPADs, we investigate the semiconductor structure design and optimization.

Low lateral divergence 2 μm InGaSb/ AlGaAsSb broad-area quantum well lasers.

High power and high brightness mid-infrared GaSb based lasers are desired for many applications, however, the high lateral divergence is still the influence factor for practical application. In this paper, a simple and effective approach based on the fishbone-shape microstructure was proposed, the effective improvement on both the lateral divergence and output power of 2 μm GaSb based broad-area lasers was demonstrated. The lateral divergence is reduced averagely by 55% and 15.

Effect of Mn, Fe and Co on the compression strength and ductility of in situ nano-sized TiB2/TiAl composites.

The element of Fe can enhance the strength of TiB2/TiAl composite, but it is detrimental to the ductility of the composite due to the existence of large bulk TiB2 phase at grain boundary. The element of Mn is beneficial to the ductility of TiB2/TiAl composite, of which the fracture strain increases from 15.9 to 17.

Observation of the fluorescence spectrum for a driven cascade model system in atomic beam.

We experimentally study the resonance fluorescence from an excited two-level atom when the atomic upper level is coupled by a nonresonant field to a higher-lying state in a rubidium atomic beam. The heights, widths and positions of the fluorescence peaks can be controlled by modifying the detuning of the auxiliary field. We explain the observed spectrum with the transition properties of the dressed states generated by the coupling of the two laser fields.

Large size self-assembled quantum rings: quantum size effect and modulation on the surface diffusion.

We demonstrate experimentally the submicron size self-assembled (SA) GaAs quantum rings (QRs) by quantum size effect (QSE). An ultrathin In0.1 Ga0.