Single-mode Laser Diode Research Articles

Sensitive methane detection based on quartz-enhanced photoacoustic spectroscopy with a high-power diode laser and wavelet filtering

Quartz-enhanced photoacoustic spectroscopy (QEPAS) based methane (CH4) detection using a high power continuous wave (CW), single mode diode laser with an emission wavelength at 2.3 μm was demonstrated. A diode laser with a high output power of 6.3 mW and a quartz tuning fork (QTF) with a low resonant frequency of 30.72 kHz were used to improve the CH4-QEPAS sensor performance. A micro-resonator and water vapor acted as a catalyst for improving the relaxation rate of the target gas molecule were added in the CH4-QEPAS sensor for further enhancing the signal level. A minimum detection limit (MDL) of such a CH4-QEPAS sensor reached 7.9 parts per million (ppm). After utilizing wavelet filtering, the signal-to-noise ratio (SNR) was improved by a factor of 3.6 and a lower MDL of 2.2 ppm was achieved. In order to evaluate the long-term stability of such a CH4-QEPAS sensor an Allan deviation analysis was implemented.

Generation of 14.0 W of single-frequency light at 770 nm by intracavity frequency doubling

We present a continuous, narrow-linewidth, tunable laser system that outputs up to 14.0 W at 770 nm. The light is generated by frequency doubling 18.8 W of light from a 1540 nm fiber amplifier that is seeded by a single-mode diode laser achieving > 74 % conversion efficiency. We utilize a lithium triborate crystal in an enhancement ring cavity. The low intensity noise and narrow linewidth of the 770 nm output are suitable for cold atom experiments.

Numerical and Experimental Analysis of Optical Frequency Comb Generation in Gain-Switched Semiconductor Lasers

We have performed a systematic experimental and simulation analysis of the optical frequency combs generated by gain-switching single mode laser diodes, either free-running or subjected to optical injection. The simulations have been produced with a dynamical model consisting of three rate equations that include stochastic noise terms. The model parameters have been extracted from experiments. An exhaustive comparison between the simulated and the experimental temporal profiles and optical spectra generated under a wide range of switching and optical injection conditions has been performed. The excellent quantitative agreement found in the entire range of the explored operating conditions supports the validity of the model for the analysis of the comb generation mechanisms. The detailed maps generated provide guidelines for selecting suitable operating conditions for specific comb characteristics.

The specifics of single-mode laser modules application in optical-electronic complexes based on light scattering

The polarization state of edge-emitting single-mode laser modules radiation and their conditions of using in laser measuring systems of scattered radiation diagnosis are considered. For laser modules from two batches, both the polarization degree of collimated radiation and polarization degree spatial dependence in two orthogonal planes when there is no collimation are measured. It is established the angular dependence of non-collimated radiation polarization degree at different planes is various. We also considered the impact laser diodes degradation on these dependencies. It is shown that while exploitation of single-mode laser diodes in laser systems for scattered radiation characteristics researching it is needed to make control the polarization state of their radiation while service.

A new control system for high-precision In-Gas Laser Ionization and Spectroscopy experiments at KU Leuven

A new automated control system is developed for the In-Gas Laser Ionization and Spectroscopy (IGLIS) laboratory at KU Leuven. The IGLIS Control System is capable of stabilizing a narrowband single-mode tunable diode laser with a standard deviation of 1.14 MHz. Furthermore, the system controls and synchronizes all data acquisition for multiple techniques from resonant laser spectroscopy in gas cell or in gas jet to atomic Planar-Laser Induced Fluorescence (PLIF) spectroscopy of copper atoms seeded in a supersonic gas jet. The IGLIS Control System is validated by measuring the hyperfine splitting parameters of the ground state transition at 327 nm in 63Cu.

Evaluation of Luminescence Properties of Single Hydrophilic Upconversion Nanoparticles by Optical Trapping

By using multifunctional optical tweezers (OT) equipped with a 980 nm continuous-wave single-mode diode laser and multiple detectors, we are able to trap single upconversion nanoparticles stably as...

Enhanced self-phase modulation effect: an effective method of generating high average and peak power femtosecond laser pulses

This work experimentally explores the important application of the enhanced self-phase modulation (SPM) effect for the generation of high average power and high peak power femtosecond laser pulses in an all-fiber mode-locked laser oscillator pumped by a single-mode laser diode. Depending on the utilization of a section of nonlinear spectral broadening fiber with a 4.2 µm mode field diameter (MFD) and the optimization of the polarization-maintaining (PM) fiber length in a polarization-based all-fiber Lyot filter, the oscillator delivers 350 mW of average power at a 46.2 MHz repetition rate, resulting in 7.5 nJ pulse energy. The laser produces SPM-broadened spectrum and the spectrum features symmetrical multi-peak distribution. The resulting compressed pulse duration and average power are 107 fs and 271 mW, respectively, which corresponds to 54.8 kW of peak power. Additionally, comparative experiments have also been performed by replacing the nonlinear spectral broadening fiber with equal-length standard fiber with 6.2 µm MFD and shortening the length of the 45° aligned PM fiber of the all-fiber polarization-based Lyot filter, respectively. The presented experimental scheme demonstrates a notable improvement in terms of average and peak power compared to conventional experimental methods. Simultaneously, the experimental scheme also shows that the enhanced SPM effect in a mode-locked fiber laser oscillator has important application value for minimizing pulse duration and lowering the mode-locking threshold.

Optical Behavior Analysis of Negative Wavelength Detuning in SMFP-LD and Its Effect on Multi-RF Generation

Injection locking with positive wavelength detuning has been used for a long time for optical signal processing, signal generation, and computing. Recently a new technique, “injection locking with negative wavelength detuning,” has been introduced and has shown its potential on microwave generation. In this paper, we analyze optical behavior of negative injection locking and its impact on multi-RF generation using single-mode Fabry-Perot laser diode (SMFP-LD). SMFP-LD is composed of a commercial multi-mode FP-LD with a built-in external cavity. As compared to conventionally used positive detuning optical injection, the negative detuning optical injection (NOI) shows advantageous differences on the suppression of the dominant mode, side modes, bistability property, and the hysteresis width. The laws of free carrier motion in the laser cavity is leveraged to explain these phenomena. Based on the analysis, the NOI in the SMFP-LD has a distinct advantage for multi-RF generation and switching RF signals. In addition, the output performances of the generated RF signal such as linewidth, power-dependent frequency shifting, and signal-to-noise ratio (SNR) are investigated.

Lidar thermometry using two-line atomic fluorescence.

In this work, Scheimpflug lidar has been combined with the thermometric technique two-line atomic fluorescence, to carry out stand-off, spatially resolved temperature measurements. Indium atoms were seeded into a modified Perkin-Elmer-burner and two tunable single-mode diode lasers with their wavelengths tuned to 410.17 and 451.12 nm were used to excite the seeded atoms. The fluorescence signal was collected using both a line-scan detector and a two-dimensional intensified CCD camera. One-dimensional flame temperature profiles were measured at different heights above a porous-plug burner, located at a distance of 1.5 m from the lidar system. The technique was also used to demonstrate two-dimensional temperature measurements in the same flame. The accuracy of the measured temperature was found to be limited mainly by uncertainty in the spectral overlap between the laser emission and the indium atom absorption spectrum as well as uncertainty in laser power measurements. With the constraint that indium can be introduced into the measurement volume, it is anticipated that the developed measurement concept could constitute a valuable tool, allowing in situ spatially resolved thermometry in intractable industrial applications, sufferings from limited optical access, thus requiring remote single-optical-port sensing.

Graphene and SESAM mode-locked Yb:CNGS lasers with self-frequency doubling properties.

We report on mode-locking of an Yb:Ca3NbGa3Si2O14 laser, which is pumped by a fiber-coupled single-mode laser diode. The shortest pulse duration obtained with a semiconductor saturable absorber mirror is 52 fs, with 75 mW of average output power. Sub-60 fs operation tunable between 1055 and 1074 nm is achieved by employing semiconductor absorbers with different characteristics. We also demonstrate passive mode-locking results with transmissive graphene saturable absorber, reaching an 85 fs pulse duration with 23 mW output power. Moreover, we present the non-phase-matched self-frequency doubling properties of this non-centrosymmetric crystal in the femtosecond regime.

Optoelectronic complex for express laser diodes lifetime prediction

This paper presents the optoelectronic complex, which provides both preparations for carrying out an express lifetime prediction of edge emitted strip single-mode laser diodes. It is shown that for this purpose the complex should consist of four operational units: an input control unit; a spectral radiation characteristics measurement unit; a laser lifetime forecasting unit and automatic processing hardware unit. The use of this complex makes it possible to predict the lifetime of a laser diode according to their spectral characteristics at the initial stage of its operation.

Estimating the Operational Lifespan of Transverse Single-Mode Laser Diodes from Their Spectral Characteristics

A way of predicting the operational lifespan of transverse single-mode laser diodes, based on analyzing the form factor of the envelope of its emission spectrum at the initial stage of operation, is proposed.

High order DBR GaSb based single longitude mode diode lasers at 2 μm wavelength * * Project supported by the National Basic Research Program of China (Nos. 2016YFB0402403, 2014CB643903) and the National Natural Science Foundation of China (Nos. 61790583, 61435012).

The GaSb-based distributed Bragg reflection (DBR) diode laser with 23rd-order gratings have been fabricated by conventional UV lithography and inductively coupled plasma (ICP) etching. The ICP etching conditions were optimized and the relationship among etching depth, duty ratio and side-mode suppression ratio (SMSR) was studied. The device with a ridge width of 100 μm, gratings period of 13 μm and etching depth of 1.55 μm as well as the duty ratio of 85% was fabricated, its maximum SMSR reached 22.52 dB with uncoated cavity facets under single longitudinal operation mode at room temperature.

Modelling the spectral characteristics of 1.5 – 1.6 μm high-power asymmetric-waveguide single-mode laser diodes

Spectral characteristics of high-power single-mode laser diodes with a radiation wavelength of 1.5 – 1.6 μm are simulated with allowance for nonlinear losses. A satisfactory agreement between the calculation and experimental results as applied to the dependence of the wavelength and radiation spectrum width on the laser pump current is demonstrated. The effect of thermal resistance of a laser diode on the active region heating, spectrum width, and radiation wavelength is considered.

Acousto-Optic Power Summation for Mutually Noncoherent Pulsed Lasers

A method of the power summation for mutually noncoherent pulsed lasers of the same type using time interleaving is proposed and validated experimentally. The method uses an acoustic-optic deflector, which commutates radiation of different sources into one output channel simultaneously with radiation presenting in this channel. It is crucially important that the power of the final output radiation is equal to the power sum of the input sources, and the angular and coordinate parameters of an output beam are the same as that for the input sources. The experiments were carried out with single-mode diode lasers on a wavelength of 1.3 μm using a ТеО2-crystal-based deflector. The method is appropriate for the power summation for fiber-optic, diode, and solid-state lasers. We have estimated the main interrelated parameters.

Fibre-optic 100 fs pulse amplification and transmission system in the telecom range

We have fabricated and investigated an efficient all-fibre source of ultrashort pulses of 100 fs duration with an energy of up to 5 nJ in the telecom range (near λ = 1.56 μm). Pulses from an erbium-doped fibre master oscillator with a minimum duration of 127 fs and repetition rate of 38.1 MHz were amplified in an erbium-doped active fibre to a maximum average power of 194.3 mW with a 30 % efficiency under pumping by 640-mW single-mode laser diodes at a wavelength λpump = 976 nm and then compressed to an ∼100 fs duration in a silica fibre with reduced nonlinearity (LMA fibre). The compressed pulses were launched with an efficiency over 80 % into a hollow-core microstructured revolver fibre (HCRF) with a cladding formed by noncontacting cylindrical silica glass capillary tubes and a 61-μm-diameter hollow core. The measured loss for the fundamental mode of this fibre was under 30 dB km−1 at λ = 1.56 μm. Owing to the weak nonlinearity and low dispersion of the HCRF, output pulses were similar in characteristics (duration and spectrum) to input pulses even at HCRF lengths above 10 m.

Compact femtosecond 10 μJ pulse energy fiber laser with a CFBG stretcher and CVBG compressor

Abstract In this work, a compact high energy fiber chirped pulse amplification system with matched pair of a chirped fiber Bragg grating stretcher and a chirped volume Bragg grating compressor is presented. Chirped pulses of 230 ps duration were amplified in a single mode Yb-doped fiber amplifiers to 10 µJ pulse energy and re-compressed to 349 fs duration corresponding to the peak power of 26 MW. Gain saturation was demonstrated when pumping with tandem of single mode laser diodes due to small mode area of the single mode fiber. Such laser source could be used in applications where high peak power is required but moderate average power is sufficient.

Continuous-wave, singly-resonant, intracavity optical parametric oscillator based on a single-mode-laser-diode-pumped Yb:KYW laser.

We report a continuous-wave (cw), intracavity, singly resonant optical parametric oscillator (ICSRO) based on an Yb:KYW laser pumped by a single-mode laser diode (LD). Pumping the ICSRO by a low-noise single-mode LD, combined with the reduced heat generation due to the lower quantum defect of the Yb:KYW laser system, effectively eliminated the onset of relaxation oscillations, which have been a long-standing problem in previous multimode-LD-pumped ICSROs, and resulted in a cw ICSRO being operated free of relaxation oscillations. At an LD power of 515mW, the generated idler power was 21mW at ∼3500 nm. To the best of our knowledge, this is the first demonstration of a single-mode-LD-pumped ICSRO.

QEPAS sensor for breath analysis: a behavior of pressure.

The measurement of trace gases has increasingly become a key technique in healthcare and other medical applications. Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a suitable method that can provide the required characteristics in such applications for a comparatively low cost and small size. The quantitative detection and a low detection limit are also required by applications. In this paper, we present new results on sensing biomedically relevant gases using the on-beam QEPAS technique with some newly developed tunable high-power single-mode laser diodes based on GaSb material. The data processing and detection limit determination are done by a field programmable gate array device, as well as an automatic measurement of the resonance frequency.

Photo-acoustic sensor based on an inexpensive piezoelectric film transducer and an amplitude-stabilized single-mode external cavity diode laser for in vitro measurements of glucose concentration

The present paper focuses on development of a compact photo-acoustic sensor using inexpensive components for glucose analysis. An amplitude-stabilized wavelength-tunable single-mode external cavity diode laser operating around 1050 nm was realized and characterized for the use of laser beam as an excitation light source. In the established setup, a fine tuning range of 9 GHz was achieved. The glucose solution was obtained by diluting D-glucose in sterile water. The acoustic signal generated by the optical excitation was detected via a chip piezoelectric film transducer. A detection limit of 50 mM (900 mg/dl) was achieved. The device may be of great interest for its applications in medicine and health monitoring. The sensor is promising for non-invasive in vivo glucose measurements from interstitial fluid.