Emitting Semiconductor Lasers Research Articles

High continuous-wave power surface emitting terahertz lasers integrated with multimode interferometer

Distributed feedback (DFB) surface emitting semiconductor laser realizes power extraction by periodic photonic heterostructure. A direct method to increase the output power is scaling up the area of active region, however, the length of the device is restricted by the coupling strength of the DFB grating. Herein we develop a high-power single-mode surface emitting scheme by monolithically integrating second-order DFB terahertz quantum cascade laser and a multimode interferometer, which can significantly enhance the optical power by increasing photon density and altering field distribution in the grating region. Application of this concept leads to high continuous-wave (CW) surface emitting power of 55 mW, with single-lobed far-field pattern and single-mode operation at about 3.9 THz, which is among the best reported results. Such an integrated scheme can be combined with any one-dimensional photonic heterostructure, which has great potential in further improving the pulsed and CW output power of single-mode semiconductor lasers.

Optimization of Oxidation for Vertical Cavity Surface Emitting Semiconductor Lasers

Optimization of Oxidation for Vertical Cavity Surface Emitting Semiconductor Lasers

Designing a 1550 nm Pulsed Semiconductor Laser-Emission Module Based on a Multiquantum-Well Equivalent Circuit Model

The demand for eye-safe 1550 nm pulsed semiconductor laser-emission modules is increasing in the field of active laser detection, owing to their long range and high precision. The high power and narrow pulse of these modules can significantly improve the distance and accuracy of active-laser detection. Here, we propose an equivalent circuit model of a multiquantum-well laser based on the structure of a laser device. We developed a design method for 1550 nm pulsed semiconductor laser-emission modules according to the equivalent circuit model of an InGaAlAs laser. In this method, the module design was divided into laser chip and laser-driver levels for optimization and simulation. At the chip level, a high-output power laser chip with optimal cavity length and optical facet coating coefficients was obtained. At the laser-driver level, the model was applied to a drive circuit to provide direct narrow optical pulses. Finally, a laser-emission module was fabricated based on the optimal design results. In addition to the power-current features of the actual laser, the critical voltage of the emission module and laser pulses were tested. By comparing the test and simulation results, the effectiveness of the proposed method was confirmed.

Leader-laggard synchronization of polarization chaos in mutually coupled free-running VCSELs.

We systematically study the leader-laggard synchronization of polarization chaos in mutually coupled free-running vertical cavity surface emitting semiconductor lasers in two cases of parallel and orthogonal injection. Specifically, we quantitatively investigate the effect of critical external parameter mismatch such as the coupling intensity and frequency detuning on the leader-laggard relationship utilizing the cross-correlation function. When the difference between two main cross-correlation peak values exceeds 0.1, the leader-laggard relationship can be viewed to be stable. Our results demonstrate that compared with the coupling strength, the frequency detuning is the dominant factor in determining the stability of the leader-laggard relationship. The exchange of the leader-laggard role occurs within a frequency detuning region from -5 GHz to 5 GHz for both parallel and orthogonal injection. Once the leader-laggard relationship is stable, the difference between the two cross-correlation values can reach 0.242 for negative frequency detuning, but the corresponding value is only 0.146 under positive frequency detuning.

Towards ultra fast pulse generation by gain-switching of diode pumped surface emitting semiconductor lasers

Towards ultra fast pulse generation by gain-switching of diode pumped surface emitting semiconductor lasers

Bistable and coexisting attractors in current modulated edge emitting semiconductor laser: control and microcontroller-based design

This paper reports on the numerical analysis, control of coexisting attractors and microcontroller-based design of current modulated edge emitting semiconductor laser (CMEESL). The stability of equilibrium points of solitary edge emitting semiconductor laser found is investigated. By varying the amplitude of modulation current density, CMEESL displays periodic behaviors, period-doubling to chaotic behavior, bistability and coexistence between limit cycle and chaotic attractors. The coexistence between chaotic and limit cycle attractors is destroyed and controlled to a desired monostable trajectory by means of the linear augmentation method. In addition, a microcontroller-based circuit is also designed to indicate that CMEESL can be used in real applications. Microcontroller-based circuit outputs and numerical analysis results confirm each other.

Synchronization of polarization chaos in mutually coupled free-running VCSELs.

We numerically demonstrate and analyze polarization chaos synchronization between two free-running vertical cavity surface emitting semiconductor lasers (VCSELs) in the mutual coupling configuration under two scenarios: parallel injection and orthogonal injection. Specifically, we investigate the effect of external parameters (the bias current, frequency detuning and coupling coefficient) and internal parameters (the linewidth enhancement factor, spin-flip relaxation rate, field decay rate, carrier decay rate, birefringence and dichroism) on the synchronization quality. Finally simulation results confirm that in the parallel injection, chaotic synchronization can reach a cross-correlation coefficient of 0.99 within a range of parameter mismatch ±12%. On the other hand, the chaos synchronization for orthogonal injection only reaches a cross-correlation coefficient of 0.95 within a range of parameter mismatch ±3%.

Design and Fabrication of 940 nm Horizontal Cavity Surface Emitting Semiconductor Laser

Design and Fabrication of 940 nm Horizontal Cavity Surface Emitting Semiconductor Laser

Theoretical modelling of single-mode lasing in microcavity lasers via optical interference injection.

The effective manipulation of mode oscillation and competition is of fundamental importance for controlling light emission in semiconductor lasers. Here we develop a rate equation model which considers the spatially modulated gain and spontaneous emission, which are inherently governed by the ripple of the vacuum electromagnetic field in a Fabry-Pérot (FP) microcavity. By manipulating the interplay between the spatial oscillation of the vacuum field and external optical injection via dual-beam laser interference, single longitudinal mode operation is observed in a FP-type microcavity with a side mode suppression ratio exceeding 40 dB. An exploration of this extended rate equation model bridges the gap between the classical model of multimode competition in semiconductor lasers and a quantum-optics understanding of radiative processes in microcavities.

Design of gain region of high-power vertical external cavity surface emitting semiconductor laser and its fabrication

<sec> The vertical external cavity surface emitting laser (VECSEL) is one of the hottest research fields of semiconductor lasers, due to its high power and good beam quality. However, there are few reports about how to systematically design the active region of VECSEL. In this paper, the gain design of quantum wells, which are the most important region within the VECSEL, is carried out. </sec><sec> To achieve low power consumption under high temperature condition, epitaxial structure of the VECSEL is optimized by using the commercial software PICS3D. Firstly, the relationship between the structure of quantum well and the gain is simulated by the <i>k</i>·<i>p</i> method. Then, the gain spectra of quantum wells at different carrier densities and temperatures are compared with each other, and the optimal composition and thickness of quantum well are thus determined. The temperature drift coefficient is 0.36 nm/K, obtained by simulating the drift of the gain peak wavelength at the working temperature. Finally, the gain spectra of quantum wells with five different barriers are compared with each other. The slight blue shift of the gain peak in the quantum well with five different barriers accommodates the different emission thermal drifts of the quantum well at high temperature operation. With the GaAsP barriers on both sides of quantum well the gain characteristics of quantum wells can be improved efficiently. </sec><sec> The designed structure is deposited by the MOCVD system. According to the reflection spectrum of the gain chip, measured by ellipsometer, the stop-band over 100 nm is centered at the about 970 nm wavelength, confirming accurate growth of the VECSEL. The 808 nm pump laser is focused on the surface of VECSEL chip at an incident angle from 30° to 50°. The VECSEL light-light characteristics are tested under the output coupling mirror with different reflectivity. The output power of VECSEL with a 97.7% reflectance output coupling mirror reaches 9.82 W at the pumping power of 35 W, without saturating the power curve. By using the external mirrors with different reflectivity, there appears the wavelength shift with the pumping power changing from 0.216 nm/W to 0.16 nm/W. Thus, the internal heating effects are different for VECSEL with different mirrors. The divergence angles at two orthogonal directions are 9.2° and 9.0°, respectively. And the circle profile of optical field shows good symmetry. </sec>

The effect of optical cooling of the SPM probe in the optomechanical resonator

Optomechanical resonators formed by the surface of an emitting semiconductor laser and the reflective surface of the probe of scanning probe microscope (SPM) were studied. The use of scanning probe microscopy techniques allowed studying the properties of such optomechanical resonators in details. The effect of optical cooling of an SPM probe in an optomechanical resonator was investigated by measuring the spectra of thermal vibrations of an SPM probe. Minimal achievable temperatures of SPM probe cooling were experimentally established.

The influence various sources of fluctuation on the statistical parameters of the vertical cavity surface emitting lasers output radiation

Based on statistical modeling, a numerical analysis of the effects exerted by different factors (fluctuations of the spontaneous emission intensity, nonequilibrium carrier concentration, injection current density) on the statistical characteristics of radiation at the output of surface emitting semiconductor lasers in the region of polarization instability has been performed. In this region the effect of fluctuations is maximal, offering the possibility for substantiated conclusions about relative effects of the parameters. In a theory of semiconductor lasers it is thought that the intensity fluctuations of spontaneous emission represent the dominant source of fluctuations, whereas all other sources may be neglected. As demonstra ted by the results of conducted statistical modeling, this statement is too rigorous; moreover, such a source is not dominant. Taking into consideration fluctuations of the carrier concentration, which result in fluctuations of the amplification factor, we can derive a complete set of the relationships observed experimentally. This result cannot be associated with features our model because in our theory spontaneous emission is a significant factor. If the influence of spontaneous emission would be the dominant factor, it would affect the simulation results. The obtained data make it possible to doubt the key role of the spontaneous emission intensity fluctuations in the process of statistical characteristics formation for the output radiation and to take into account fluctuations of the nonequilibrium carrier concentration.

Comparison of single-side and double-side pumping of membrane external-cavity surface-emitting lasers.

We studied and compared single-side pumping (SSP) and double-side pumping (DSP) of a semiconductor membrane external-cavity surface-emitting laser (MECSEL). The MECSEL-active region was based on an AlGaAs quantum well structure embedded between two silicon carbide (SiC) wafer pieces that were used as transparent intra-cavity (IC) heat spreaders creating a symmetrical cooling environment. The gain structure targeted emission at 780 nm, a wavelength region that is important for many applications, and where the development of high-brightness high-power laser sources is gaining more momentum. By DSP at 20°C heat sink temperature, we could reduce the laser threshold from 0.79 to 0.69 W of absorbed pump power, while the maximum output power was increased from 3.13 to 3.22 W. The differential efficiency was improved from 31.9% to 34.4%, which represents a record value for SiC-cooled vertically emitting semiconductor lasers. The improvements are enabled by a reduced thermal resistance of the gain element by 9% compared to SSP. The beam quality was measured to be M2<1.09. Finally, we demonstrate a maximum tuning range from 767 to 811 nm. This wavelength range was not addressed by any MECSEL or vertical external-cavity surface-emitting laser device before and extends the available wavelengths for semiconductor based high-quality beam and high-power laser sources to a wavelength window relevant for quantum technology, spectroscopy, or medicine.

Continuous repetition rate tuning from 960 MHz to 1.72 GHz of a sub-300 femtosecond mode-locked semiconductor disk laser

Dataset supports: Chen Sverre, T. et al (2018). Continuous repetition rate tuning from 960 MHz to 1.72 GHz of a sub-300 femtosecond mode-locked semiconductor disk laser. Applied Physics Letters, 113(16), [161106].Vertical External Cavity Surface Emitting semiconductor Lasers rely on Semiconductor Saturable Absorbing Mirrors for mode-locking, allowing laser cavities to be designed far from stability limits. We have harnessed this feature to study repetition rate tunability. The cavity element separations were determined by a coded cavity design protocol based on cavity round trip matrix calculations. We produced a sub-300-fs near transform-limited pulse train with a repetition rate of 0.96 MHz - 1.72 GHz, at 1035 nm and average power of 50 mW.

Chirped photonic crystal for spatially filtered optical feedback to a broad-area laser

We derive and analyze an efficient model for reinjection of spatially filtered optical feedback from an external resonator to a broad area, edge emitting semiconductor laser diode (DL). Spatial filtering is achieved by a chirped photonic crystal, with variable periodicity along the optical axis and negligible resonant backscattering. The optimal chirp is obtained from a genetic algorithm, which yields solutions that are robust against perturbations. Exemplary numerical simulations of the composite system with our optoelectronic solver indicate that spatially filtered reinjection can enhance lower-order transversal optical modes in the DL and, consequently, improve the spatial beam quality.

Experimental study of optical frequency comb generation in gain-switched semiconductor lasers

A systematic experimental study of the generation of Optical Frequency Combs (OFCs) by gain switching two types of edge emitting semiconductor lasers (Distributed Feedback and Discrete Mode) is presented. High resolution spectral measurements together with linewidth characterization and the analysis of the temporal profiles and the radio-frequency spectra are used to evaluate the evolution of the quality of the OFCs, as a function of the driving conditions. Different types of emission spectra are identified. The physical origin of the OFC properties is discussed. The results indicate that the driving conditions rather than the device properties determine the OFC quality. The optical injection is demonstrated to either improve or deteriorate the quality of the OFCs generated by gain switching, depending on the injection conditions.

Stabilization of broad-area semiconductor laser sources by simultaneous index and pump modulations.

We show that the emission of broad-area semiconductor amplifiers and lasers can be efficiently stabilized by introducing two-dimensional periodic modulations simultaneously on both the refractive index and the pump (gain-loss) profiles in the transverse and longitudinal directions. The interplay between such index and gain-loss modulations efficiently suppresses the pattern-forming instabilities, leading to highly stable and bright narrow output beams from such sources. We also determine the stabilization performance of the device as a function of the pump current and linewidth enhancement factor.

Stochastic Differential Equation Model for Spontaneous Emission and Carrier Noise in Semiconductor Lasers

We present a new stochastic differential equation model for the spontaneous emission noise and carrier noise in semiconductor lasers. The correlations between these two types of noise have often been neglected in recent studies of the effects of the noise on the laser dynamics. However, the classic results of Henry show that the intensity noise and the carrier noise are strongly negatively correlated. Our model demonstrates how to properly account for these correlations since the corresponding diffusion coefficients agree exactly with those derived by Henry. We show that in fact in the correct model the spontaneous emission noise and the carrier noise are driven by the same Wiener processes. Furthermore, we demonstrate that the nonzero correlation time of the physical noise affects the mean dynamics of both the electric field amplitude and the carrier number. We show that these are systematic corrections that can be described by additional drift terms in the model.

Optomechanical coupling between AFM cantilever and semiconductor laser

Optomechanical coupling between cantilever of the atomic force microscope (AFM) and a semiconductor laser was studied. When an AFM cantilever is oriented parallel to the surface of the emitting semiconductor laser, the system forms an optomechanical resonator. The optomechanical coupling due to photothermal effect was shown in room conditions. By optomechanical cooling the effective temperature of Si3N4 cantilever was reduced down to 80 K. Amplitude-to-phase conversion in the studied cavity was demonstrated.

Dynamic modelling of electrooptically modulated vertical compound cavity surface emitting semiconductor lasers

A generalized rate equation model is used to simulate the interrelated amplitude and frequency modulation properties of Electrooptically Modulated Vertical Compound Cavity Surface Emitting Semiconductor Lasers in both large and small signal modulation regimes. It is shown that the photon lifetime in the modulator subcavity provides the ultimate limit for the 3 dB modulation cutoff frequency. It is shown that there is an optimum design (number of periods) of both the intermediate and top multistack reflectors to maximise the large-signal modulation quality.