Single-mode Laser Diode Research Articles

Nonlinear dynamics of a laser diode subjected to both optical injection and optical feedback.

We analyse theoretically the nonlinear dynamics of a single-mode laser diode subjected to both optical injection and optical feedback. Detailed mappings of the laser dynamics reveal that, due to optical feedback (OF), the locking boundaries resulting from optical injection (OI) shift towards larger negative detunings and higher injection rates and display a periodic pattern of the injection locking boundaries. We demonstrate how feedback induces a cascade of quasiperiodic bifurcations associated with abrupt dynamic changes, hence altering the route to locking. A close inspection of the laser optical spectra for increasing feedback rate reveals the complex interplay between undamped relaxation oscillations and external cavity frequencies.

Robust design of mid-infrared GaSb-based single-mode laser diode fabricated by standard photolithography with socketed ridge-waveguide modulation.

In this paper, we put up a robust design of a stable single-mode-operated GaSb-based laser diode emitting around 1950nm. This novel design structure with socketed ridge-waveguide enables a simple fabrication and batch production of mid-infrared laser diodes on account of the mere usage of standard photolithography. By introducing micron-level index perturbations distributed along the ridge waveguide, the threshold gains of different FP modes are modulated. Four geometrical parameters of the perturbations are systematically optimized by analyzing the reflection spectrum to get a robust single-mode characteristic. Based on the optimized geometrical parameters, 1-mm long uncoated lasers are carried out and exhibit a stable single longitudinal mode from 10 °C to 40 °C with a maximum output power of more than 10 mW. Thus, we prove the feasibility of the standard photolithography to manufacture the monolithic single-mode infrared laser source without regrowth process or nanoscale lithography.

28.1: Invited Paper: A Review of Optical source by using μLED and Single mode Laser Diodes for HMD, AR/VR Glasses

Expansion of devices to access the virtual world is expected due to much attention to Metaverse in recent years. In particular, head mount display (HMD), smart glasses and AR glasses have been attracting attention as next‐generation mobile devices that will replace smart phones. Laser diodes and μLEDs are developed in various research institutes and companies as light sources for those devices. In this paper, we describe the development status of the laser diodes and the μLEDs, the technical problems of optimal adaptation to smart glasses, and introduce one of the solutions when using the laser diodes.

Diode-pumped mode-locked Yb:Sc2SiO5 laser generating 38 fs pulses.

We report on sub-40 fs pulse generation from a Yb:Sc2SiO5 laser pumped by a spatially single-mode fiber-coupled laser diode at 976 nm. A maximum output power of 545 mW was obtained at 1062.6 nm in the continuous-wave regime, corresponding to a slope efficiency of 64% and a laser threshold of 143 mW. A continuous wavelength tuning across 80 nm (1030 -1110 nm) was also achieved. Implementing a SESAM for starting and stabilizing the mode-locked operation, the Yb:Sc2SiO5 laser delivered soliton pulses as short as 38 fs at 1069.5 nm with an average output power of 76 mW at a pulse repetition rate of ∼79.8 MHz. The maximum output power was scaled to 216 mW for slightly longer pulses of 42 fs, which corresponded to a peak power of 56.6 kW and an optical efficiency of 22.7%. To the best of our knowledge, these results represent the shortest pulses ever achieved with any Yb3+-doped rare-earth oxyorthosilicate crystal.

L-band dual-comb based on gain-switched lasers for CO2 monitoring

This paper reports the development of a dual-comb spectroscopy system based on gain-switched single-mode laser diodes emitting at 1572 nm. The switching is performed by a train of short electrical pulses at a repetition rate of 100 MHz while the lasers are subjected to external optical injection. Under these conditions, broad and Hat optical frequency combs (OFC) are generated, showing 500 tones within 10 dB and a line spacing fix ed by the repetition rate of the swi tching pulses. The dual-comb gene rated by th e interference of two such combs with slightly different line spacing, is used for measuring the absorption line of CO2 at 1572.02 nm. The transmission spectrum is analyzed and fitted to a Voigt profile. A deviation of 3% in the residuals of the fitting is obtained, denoting the high spectral performance of the spectroscopy system.

Simulating the process of steady-state thermoreflectance for measuring the thermal conductivity of materials

The measurement of thermal conductivity by the method of steady-state thermoreflectance is based on the effect of heating the sample by laser radiation. The power of reflected radiation from the sample is measured using an additional probe laser. The change in the reflection coefficient of the studied material due to the heating is proportional to the change of the sample temperature. The radiation power absorbed by the material acts as a volumetric heat source. The value of thermal conductivity is calculated according to the Fourier’s law of thermal conductivity. A steady-state thermoreflectance setup requires calibration, i.e., thermal conductivity measurement of reference samples. The value of the calibration coefficient, in turn, depends on the characteristics of the lasers used in the setup. In this work, a numerical model of sample heating is proposed which allows considering the shape and diameter of the incident radiation beam, the distribution of radiation power over the beam area, and the absorption and reflection coefficients of the material. A methodology for samples reflection and absorption coefficients determination, including measurements and calculations considering the Fabry-Perot effect, is proposed. The study was performed for the samples of germanium, silicon, gallium arsenide, and sitall. The irradiation was performed with a continuous wave single-mode diode laser with a wavelength of 980 nm. The incident radiation power distribution over the beam area was approximated according to the Gaussian function in the OriginPro software. The radiation power that passed through the samples and reflected from them was measured. The temperature of the samples during irradiation was measured with a thermal imager. The reflection and absorption coefficients of the samples were determined from the results of radiation power measurements using a mathematical model of the interaction of plane-polarized TE electromagnetic radiation with the material. Comparison of the calculation results with the literature data for germanium, silicon, and sitall samples showed their correspondence. For gallium arsenide there was a discrepancy between the calculation results and the literature data. For gallium arsenide samples, a model considering the Fabry-Perot effect was used, and the optical properties were determined numerically by searching for the minimum modules of the transfer functions of the transmitted and reflected radiation in the Matlab program. The model of electromagnetic heating of the investigated samples was implemented in the COMSOL Multiphysics software. A method for the determination of the reflection and absorption coefficients of materials investigated by the steady-state thermorflectance is proposed. The proposed model allows considering beam shape, width and distribution of the radiation power as well as the value of the absorbed radiation power for each sample. The difference between the calculated values of the sample temperature and the measurement results does not exceed 9 %. The model can be applied to measure the thermal conductivity of bulk and thin-film materials with unknown properties.

Single mode laser diode based compact seed source for continuous wave Yb-Raman fiber amplifier with enhanced higher order Raman suppression

In this paper, we demonstrated a novel seed source for the continuous wave Yb-Raman fiber amplifier, which adopted an 1140 nm single mode laser diode (LD) as Raman signal seed and a conventional 1085 nm fiber oscillator as the Raman pump seed. By splicing a section of long passive fiber in the Raman pump seed cavity, optimizing the Raman pump seed power and the cooling condition, the higher order Raman threshold was doubled and over 500 W output Yb-Raman fiber amplifier was achieved. In addition, our experiment also proved that, for the first time, splicing long passive fiber in the seed oscillator cavity improved the temporal performance of the first order Raman in the conventional fiber master oscillator power amplifier, which could increase the higher order Raman threshold as a result. The seed structure based on a single mode LD and a long cavity length fiber oscillator, could provide a highly compact and cost effective seed source for the high power Yb-Raman fiber amplifier with enhanced higher order Raman suppression.

A 1030 nm all-PM SESAM mode-locked dissipative soliton fiber oscillator and its amplification with Yb-doped fiber and a Yb:YAG thin rod

In this research, an all- polarization-maintained semiconductor saturable absorber mirror (SESAM) mode-locked fiber oscillator and its amplification by Yb-doped fiber and a Yb:YAG thin rod are presented. From a ring-type cavity configuration created with commercially accessible components, including SESAM, the dissipative soliton fiber oscillator exhibits stable mode-locking near 1030 nm. Subsequent three-stage fiber amplifiers pumped by single-mode fiber-coupled laser diodes and a single-stage Yb:YAG thin-rod amplifier boost the output power to 11.3 W at a repetition rate of 495 kHz. After pulse compression, a pulse duration of 758 fs is achieved with output power and pulse energy levels of 9 W and 18.2 μJ, respectively.

High-Resolution Simulation of Externally Injected Lasers Revealing a Large Regime of Noise-Induced Chaos

We present comprehensive numerically simulated scans of the spectral evolution of the output from a single-mode semiconductor laser diode undergoing external light injection. The spectral scans are helpful to understand the different regimes of operation as well as the system evolution between each state: i.e., locked state, four-wave mixing, pulsations, chaos. We find that, when under strong injection, when the injected power equals about half of the laser power, two distinct regions of chaotic behaviour are observed. One of the chaotic regions arises due to the usual period-doubling route to chaos; the other chaotic region is a blurring of what would be higher-order period pulsations whose periodicity is broken by spontaneous emission and the laser spectrum is chaotic. Eliminating spontaneous emission in our simulations confirms the latter chaotic region becomes a region with higher-order pulsations.

Ultra-Low Threshold and Temperature-Stable InGaN Blue and Green Laser Diodes

We report on AlInGaN-based blue and green edge-emitting lasers designed for low-current operation and low power consumption. By properly optimizing cavity length and mirror coatings, threshold currents below 5 mA are achieved on single-mode blue laser diodes (LDs) emitting at 460 nm. For output power levels below 10 mW, the LDs with an optimized chip design exhibit a decreased power consumption and an increased power stability against temperature variations compared to LDs with a standard chip design. Extended to green emitters, the new design results in single-mode LDs emitting at 515 nm with threshold currents close to 15 mA.

Polarization stability of the single-mode laser diodes radiation applied in radiation scattering study complexes

Key features of semiconductor lasers and its serially manufacturing technology modernization have greatly expanded of its using at applied studies at last 20 years. But there is set of factors restricting such lasers application in a number of optical-electronic measuring complexes. Particularly in particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) complexes commonly the gas and solid-state lasers is used due to more stability of spectral, energy and polarization characteristics of radiation then semiconductor lasers have. However gradual introduction of the serially manufacturing laser diodes into such systems picking up the pace that certainly characterizes the progress of reaching the required stability of its output laser radiation parameters. In laser measurement systems where medium investigation carried out by analyzing of scattering radiation in it the probe radiation polarization is often important. So the using in such systems the laser diodes as sources of radiation need to be followed by stability monitoring of its polarization characteristics which may be violated both by the outer factors and by natural degradation of inner laser diode structure. This work is devoted to the issues of monitoring the radiation polarization characteristics of the serially manufacturing single-mode laser diodes.

Prediction of life time of high-power IR laser diode by resolution of its spectrum to single-mode components

The paper proposes a method for predicting the service life of high-power laser diodes used in optoelectronic measuring systems which allow adjusting the thermophysical parameters of the diagnosed flow volume in a certain range of their values. The method based on the analysis of the current dependence of the shape of the line enveloping the laser radiation spectrum after 200 hours of their operation. It is shown that for such an analysis the emission spectrum must be considered as a superposition of the emission spectra of single-mode laser diodes.

Optimization of power supply mode of single-mode laser diode by ratio of current and integral spectrum parameter

Bursting development of the technological base of semiconductor quantum electronics determined the width of the domain for use of semiconductor lasers in optical-electronic measuring systems based on the optical methods of stream research. In order to improve the accuracy of such systems, it is proposed to use a simple technique for optimizing the supply mode of a single-mode laser diode, based on an analysis of the current dependence of its integral spectral parameter. It is shown that the optimal value of the pumping current appears when the radiation spectrum envelope line tends to match the normalized Gaussian curve within the width of the spectral line.

Distributed Temperature Monitoring Inside Ytterbium DFB and Holmium Fiber Lasers

A distributed temperature monitoring inside a cavity of ytterbium DFB and holmium fiber lasers has been demonstrated with a spatial resolution of 1 and 5 mm, respectively, for the first time to the best of our knowledge. For this, we use an optical backscatter reflectometer, which measures intracore temperature, and compare it with the data of an IR thermographic camera, which measures temperature from the surface of a fiber. In the case of holmium fiber laser pumped at a wavelength of 1125 nm with a power of 6 W, the maximum temperature variation along the ∼3-m active fiber reaches ∼60 °C. In the case of ytterbium DFB laser, we observe a strong inhomogeneity of the temperature along the DFB cavity, which leads to a significant decrease in the lasing efficiency. When pumped by a single-mode laser diode at a wavelength of 976 nm with a power of up to 526 mW, the maximum temperature difference reaches 37 °C for the 37-mm DBF cavity.

A PLATFORM FOR ULTRA-COLD EXTERNAL CAVITY DIODE LASERS

We report on the construction of a platform for ultra-cold tuneable external cavity diode laser system working well below the room temperature (-75 0C) under rough vacuum (28mBar). A theoretical procedure is also presented to calculate thermal control parameters including heat transfer rate, thermal isolation and heat dissipation of the system. Temperature tuning capability of the system was examined utilizing a 658nm (AlGaInP) single mode laser diode. With the system designed the temperature dependent tuning range was expended to almost two fold while halving the bandwidth regarding to its room temperature performances.

Monitoring the Growth of a Microbubble Generated Photothermally onto an Optical Fiber by Means Fabry-Perot Interferometry.

In the present paper, we show the experimental measurement of the growth of a microbubble created on the tip of a single mode optical fiber, in which zinc nanoparticles were photodeposited on its core by using a single laser source to carry out both the generation of the microbubble by photothermal effect and the monitoring of the microbubble diameter. The photodeposition technique, as well as the formation of the microbubble, was carried out by using a single-mode pigtailed laser diode with emission at a wavelength of 658 nm. The microbubble’s growth was analyzed in the time domain by the analysis of the Fabry–Perot cavity, whose diameter was calculated with the number of interference fringes visualized in an oscilloscope. The results obtained with this technique were compared with images obtained from a CCD camera, in order to verify the diameter of the microbubble. Therefore, by counting the interference fringes, it was possible to quantify the temporal evolution of the microbubble. As a practical demonstration, we proposed a vibrometer sensor using microbubbles with sizes of 83 and 175 µm as a Fabry–Perot cavity; through the time period of a full oscillation cycle of an interferogram observed in the oscilloscope, it was possible to know the frequency vibration (500 and 1500 Hz) for a cuvette where the microbubble was created.

Nonlinear Dynamics Induced by Optical Injection in Optical Frequency Combs Generated by Gain-Switching of Laser Diodes

We present experiments and numerical simulations of optical frequency combs generated by gain-switching a single mode laser diode when subject to optical injection. Our analysis focuses on the combs with a frequency separation fR in the GHz range. We present experimental maps in the parameter space spanned by the detuning and the strength of the optical injection that identify the boundaries between regions with different dynamical states. A rich variety of nonlinear behaviors including injection-locked, unlocked and irregular combs are observed and analyzed. The dynamical state corresponding to an injection locked comb, PN, is characterized by an optical phase oscillation with a well defined amplitude in such a way that repeats or changes in 2π with an N/f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> period, where N is a natural number. Different regions of locked combs with a tongue shape around detuning values given by multiples of f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> appear in the maps. P1 and P2 are the most widespread locked states for large values of the modulation amplitude. As this amplitude decreases a much larger variety of PN states with large values of N appear in small area regions of the map. Our numerical simulations are in very good agreement with experimental results.

Extending the spectral region of a sub-terahertz spectroscopic system by mixing broad-area and single-mode laser beams

The photomixing technique is applied to a sub-THz spectroscopic system with a continuous wave multimode laser diode (CW-MLD) to extend its spectral range. For the MLD, a broad-area laser diode (BLD) is employed to produce broad continuous spectrum signals. By mixing the light from the BLD with light from a continuous wave single-mode laser diode, a new broad continuous component is generated in the higher frequency region (0.4–1.0 THz) of the Fourier spectrum of the signal waveform. This is achieved via a simple and low-cost experimental setup using laser diodes and fiber optics. Spectroscopic measurement of a Si wafer in the frequency range below 1 THz is demonstrated.

Low-Noise Carrier-Envelope-Offset-Stabilized Yb:CaF2 Oscillator

We demonstrate a carrier-envelope-offset-stabilized, self-referenceable Yb:CaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> oscillator pumped by a single-mode laser diode. By exploiting mode-locking regime based on simultaneous action of the SESAM and the Kerr lens effect we achieved self-starting generation of 85 fs pulses with a peak power approaching 47 kW. The carrier-envelope offset detection scheme was based on a standard f-to-2f interferometer with a spectral broadening in a highly nonlinear photonic crystal fiber. By employing a pump current feedback locking technique we achieved an in-loop integrated phase noise reaching 67 mrad in the 1 Hz - 1 MHz range. This exceptionally stable operation was enabled by a single-mode pump diode exhibiting intrinsically low-noise characteristics.

Lasing Characteristics of Single-Mode Laser Diode Arrays at Spectral Combining of Beams

Lasing of an array of 30 single-mode laser diodes with different wavelengths is experimentally investigated in the scheme of spectral beam combining. The maximum lasing power of 7.2 W is obtained in the pulsed mode with the quality of the combined beam close that of a single diode at the total lasing spectrum width of about 40 nm and the spectral component line widths below 0.3 nm.