In the scope of a computational experiment, high-contrast gratings (HCG) formed on a silicon- on-insulator (SOI) platform within vertical-cavity surface-emitting lasers (VCSELs) were studied for multispectral laser sources. A simulation model for spectral characteristics calculation is proposed, which includes two heterogeneously integrated parts of the VCSEL: 1) the lower output mirror based on a HCG grating in the silicon layer of the SOI surrounded by air cavities to enhance the contrast of the HCG; 2) the semiconductor VCSEL structure with an air aperture for current and optical confinement. Comparative analysis results of the spectral characteristics of VCSEL-SOI structures for zeroth, first, and second-order modes, which can be excited in the air aperture of the VCSEL, are presented. It is demonstrated that the HCG, acting as one of the cavity mirrors, effectively discriminates the VCSEL higher-order modes. An algorithm for calculating HCG parameters that ensure the maximum reflectivity at a fixed thickness of the silicon layer of the SOI is developed.

In this study, the morphology and crystallographic properties of thin titanium (Ti) films grown on atomically smooth gallium arsenide (GaAs) substrates are examined. The films were grown by direct current magnetron sputtering in an argon (Ar) flow. The surface is found to be atomically smooth with steps up to 0.1 nm in height and a morphology close to that of the Ti film substrate with nominal thicknesses of 5 and 10 nm. Increasing the film thickness to 60 nm leads to a noticeable surface reconstruction, associated with the formation of clusters up to 16 nm in height. As per X-ray diffraction studies, all films show a crystal structure of the alpha-Ti phase. In this case, an increase in the crystallite size from 7 to 20 nm and an increase in the film nominal thickness from 5 to 60 nm are also typical. Based on atomic force microscopy analysis, a change is observed in surface morphology. When the film thickness increases from 10 to 60 nm, clusters are formed on the Ti film surface, measuring 1 mu m in diameter and 16 nm in height.

We have developed a numerical model and analyzed the waveguide properties of III-V/SOI structures for the creation of injection laser sources at wavelengths ranging from 1260 to 1600 nm. We studied the transmission coefficients of hybrid laser modes propagating from III-V/SOI to SOI waveguide in a three-dimensional waveguide with variable dimensions. The model enables the three-dimensional waveguide design optimization.

A computational study of high-contrast gratings (HCG) in a vertical-cavity surface-emitting laser (VCSEL) on silicon-on-insulator (SOI) for multispectral laser sources is performed. The simulation model analyzes reflectivity of the HCG grating, formed in the SOI device layer. HCG filters higher-order modes, optimizing VCSEL performance. An algorithm is developed to determine HCG parameters, maximizing reflectivity with a SOI silicon layer fixed thickness.

An approach is developed to study temporal behavior of the active region overheating in high-power semiconductor lasers (λ = 1060 nm) with an ultrawide aperture (800 μm) operating in a quasi-continuous regime of pumping by current pulses with an amplitude of 21 A, a duration of 1 ms, and a repetition rate of 10 Hz. The approach is based on measuring the lasing dynamics with spectral selection. The lasing spectrum analysis shows that the region of the rising edge, where the amplitude of the current pulse increases, is characterized by a maximum red-shift rate of 30 nm ms–1, which is due to both thermal and nonthermal effects. The pulse region corresponding to a constant pump current amplitude is characterized only by a thermal red shift of the lasing spectrum long-wavelength edge at a rate of ~1 nm ms–1. The obtained experimental active region overheating is 2.78°C for the constant pump current amplitude range, which agrees with the calculated overheating of 3.08°C for the pump conditions under study.

We employed the selective-area-epitaxy technique using metalorganic chemical vapor deposition to fabricate and study samples of semiconductor heterostructures that incorporate highly strained InGaAs quantum wells (980–990 nm emission wavelength). Selective area epitaxy of InGaAs quantum wells was performed on templates that had a patterned periodic structure consisting of a window (where epitaxial growth occurred) and a passive mask (where epitaxial growth was suppressed), each with a width of 100 µm for every element. Additionally, a selectively grown potential barrier layer was included, which was characterized by an almost parabolic curvature profile of the surface. We conducted a study on the influence of the curvature profile of the growth surface on the optical properties of InGaAs quantum wells and the spatial distribution of composition in an ultrawide window. Our results showed that, under fixed selective-area-epitaxy conditions, the composition of the InxGa1−xAs and the wavelength of the quantum-well emission changed across the width of the window. Our study demonstrates that increasing the curvature profile of the growth surface of highly strained quantum wells leads to a transition in the photoluminescence wavelength distribution profile across the window, from quasi-parabolic to inverted parabolic.

The main results of the studies on designing high-power semiconductor laser diodes based on asymmetric semiconductor heterostructures InGaAs(P)/Al(In)GaAs(P)/GaAs with low internal optical loss, whose concept was proposed at the Ioffe Institute, are described in detail. The basic technological approaches to designing highly strained active laser media for the spectral range up to 1100 nm are considered. The results of studying the cw high-power multimode semiconductor lasers, emitting in the wavelength ranges of 780–850, 900–980, and 1000–1100 nm; high-power pulsed semiconductor lasers; and high-power lasers with a very wide emitting aperture are considered. The key factors, determining the saturation of the output optical power of high-power semiconductor lasers, are determined.

The study considers ridge waveguide characteristics in context of achieving maximum power and single-mode lasing. The watt-ampere and current-voltage characteristics, the spectrum, the radiation divergence along both axes depending on the pump current are measured, the dependences of the threshold current and differential efficiency vs the resonator length are plotted, the losses and the internal quantum yield are determined. Laser diodes with 2000 um resonator length showed the highest optical power – 190 mW at 375 mA pump current.

We report the development of laser diode microarrays with a cavity length of 6 mm, which include emitting regions 5 × 100 μm in size with a fill factor of 25

The effect of the active region design on the vertical far-field divergence is studied for high-power laser diodes based on asymmetric heterostructures with a 4-μm thick waveguide and active region designs based on single (SQW) and double (DQW) InGaAs quantum wells. It is shown that the number of quantum wells has a significant effect on the divergence determined by the angle with the 95

We report a study of electrical and optical characteristics of a new emitter design based on a vertical stack of a laser diode minibar (LDMB) and a 2D multielement thyristor array (2D META) as a high-current switch designed for the generation of short (tens of nanoseconds) high-power laser pulses. It is found that a reduction of the anode contact size of single 2D META elements down to 200 μm provides conditions for the uniform inclusion of all the elements. It is shown that in the regime of “long” pulses (14.6 ns), the peak laser power reaches 85 W at a wavelength of 1060 nm, which corresponds to a peak current of 119 A, generated in the vertical stack circuit (19.8 A per single 2D META element); in this case, the maximum pulse repetition rate for an operating voltage of 15 V reaches 700 kHz. In the regime of “short” pulses (6.4 ns) at a repetition rate of 1 MHz, the peak optical power reaches 47 W at the same wavelength, which corresponds to a generated peak current of 60 A (10 A per single 2D META element). It is shown that in both operation modes, the characteristics of the 2D META as a high-current switch do not change with increasing repetition rate.

An approach aimed at increasing the radiative efficiency in heterostructures operating in a single vertical mode at 1060 nm has been studied. Two types of heterostructures-the STJH (single tunnel junction heterostructure) and DTJH (double tunnel junction heterostructure)-have been developed to obtain the operation of a single waveguide mode of the first and second order, respectively. A multiple increase in the injection efficiency is realized by using tunnel junctions (TJs) embedded in the wide-gap barriers and placed between the active regions. An internal quantum efficiency of close to 100% and a transparency current density of 78 A/cm2 is demonstrated for both types of heterostructures, while the internal optical loss is 5.2 and 3.8 cm-1 for STJH and DTJH, respectively. The maximum radiative efficiency (for the initial linear part of the light-current curve) and the output optical power (for the current pulse of 1 µs and 9.6 A) reach 1.6 W/A and 7.8 W for STJH and 2.2 W/A and 15.8 W for DTJH.

A heterostructure design aimed at a multiple increase of the l060nm laser output efficiency is proposed. To multiply the internal and external quantum efficiency, tunnel p-n junctions (T J) were placed in the waveguide. Designed and MOCVD-grown heterostructures including two TJs demonstrate. Fabricated laser diodes demonstrate a stable second-order mode operation and a slope efficiency of 2.4W / A.

The threshold conditions and operating efficiency of a semiconductor laser emitter with a large rectangular cavity (1 × 1 mm) based on an AlGaAs/GaAs/InGaAs heterostructure for high-power stripe lasers, which operate on high-Q internally circulating structures are estimated. Two designs of emitters with different characteristics of the laser-radiation propagation regions are proposed, and the possibility of achieving a differential efficiency that is characteristic of high-power stripe lasers (more than 70%) is shown.

Ridge-waveguide semiconductor lasers operating in CW up to 500 mW with one TE00 mode and up to 2 W with few TE modes at RT are demonstrated. Highly dense arrays with stable Gaussian lateral far field (10 emitters, $200\ \mu\mathrm{m}$ total aperture) are shown to demonstrate 5 W in CW and 25 W in pulsed mode at RT.

The effect of an external resonator on the operation of a single-mode stripes laser bar based on an asymmetric InGaAs/AlGaAs/GaAs heterostructure is studied. It is shown that the external resonator increases the efficiency of optical coupling between bar stripes and to obtain laser generation in a high-order common mode with radiation pattern individual lobes about 1 deg.

In order to stabilize the lateral far-field profile of a broad area laser diode at high pump currents, the design of an asymmetric InGaAs/AlGaAs/GaAs laser heterostructure was developed. Lasers with an aperture formed by ten optically uncoupled ridge waveguides (each 6.5 μm wide) were developed on its basis. To maintain the single-mode operation of each ridge waveguide without coupling between emitters, a High Dense Microstripe Array (HDMSA, the pitch is 13.5 μm) and a Low Dense Microstripe Array (LDMSA, the pitch is 40 μm) were fabricated with a coupling parameter between adjacent lateral waveguides of 2·10 −5 and 3·10 −19 , respectively. The maximum optical output power was 5 W (HDMSA) in CW mode and 25 W (HDMSA) and 26 W (LDMSA) in pulsed mode (130ns/1kHz). It is shown that in both CW and pulsed modes, lasers of both designs provide a stable Gaussian-like distribution in the lateral far field (LFF) with a FWHM of 8–11 degrees for HDMSA and 6.5–10 degrees for LDMSA. It was found that the LFF broadens with a pump current in the range of low currents and stabilizes in the range of high currents for both designs. Studies of the near field in both operating modes at any pump currents showed no array modes and the uncoupling mode is maintained for ridge waveguide arrays.

The temporal behavior of an optical power at different moments of pulse in the far field is studied for a laser array $(\lambda=1060\ \text{nm})$ based on InGaAs/AlGaAs/GaAs. An array of narrow-stripe laser diodes with a straight ridge of $6.5-\mu\mathrm{m}$ width and a $13.5\ \mu\mathrm{m}$ -wide pitch without distributed feedback elements demonstrates that despite the strong optical coupling between adjacent array elements the lateral far fields only slightly differ from each other in width at half maximum (FWHM) (by $\pm 0.5^{\circ}$ ) at different moments of the pulse (130 ns/1 kHz) at a pump current amplitude of 5 A.

Semiconductor lasers with a 10-μm-wide lateral mesa-stripe waveguide are developed, and their radiative characteristics are studied. It is shown that the continuous wave (cw) optical power of lasers with a 4.6-mm-long cavity reaches 2.6 W at a heat-sink temperature of 25°C. Lasers with shorter cavities (<3 mm) showed lower maximum optical powers due to thermal rollover of the light–current characteristic.

Threshold conditions and efficiency analsis of a semiconductor laser emitter with a large (1x1mm) rectangular resonator based on AlGaAs/GaAs/ InGaAs heterostructures for high-power strip lasers operating on high-Q internally circulating structures is presented. Two designs of emitters with different laser radiation propagation region characteristics are proposed, and the possibility of differential efficiency characteristic as high as high-power broad lasers (70% and more) is demonstrated.