Gain-switched Diode Research Articles

Repetition Rate Optimized 2 μm Gain-Switched Diode Pumped MIR Supercontinuum

Repetition Rate Optimized 2 μm Gain-Switched Diode Pumped MIR Supercontinuum

Design guidelines for ultrashort pulse generation by a Mamyshev regenerator.

We study numerically the possibility of using various gain-switched seed laser pulse parameters and fibers for a low-cost, all-fiber Mamyshev regenerator scheme. We find that for increasing pulse durations, sufficient spectral broadening will be difficult to achieve in practice and careful design of the system parameters is required for the regenerator to function. Furthermore, an optimal input peak power level can be defined for a given fiber and pulse duration that results from a balance of competing Kerr effect and stimulated Raman scattering. We also demonstrate experimental results of 3 ps pulse generation seeded by an 80 ps gain-switched diode. Our results pave the way for designing pulse-on-demand picosecond scale fiber sources for applications.

High-power femtosecond pulses without a modelocked laser.

We demonstrate a fiber system which amplifies and compresses pulses from a gain-switched diode. A Mamyshev regenerator shortens the pulses and improves their coherence, enabling subsequent amplification by parabolic pre-shaping. As a result, we are able to control nonlinear effects and generate nearly transform-limited, 140-fs pulses with 13-MW peak power-an order-of-magnitude improvement over previous gain-switched diode sources. Seeding with a gain-switched diode results in random fluctuations of 2% in the pulse energy, which future work using known techniques may ameliorate. Further development may allow such systems to compete directly with sources based on modelocked oscillators in some applications while enjoying unparalleled robustness and repetition rate control.

Freely Triggerable Picosecond Pulses From a DBR Ridge Waveguide Diode Laser Near 1120 nm

In this letter, we present results on the pulsed operation of a distributed Bragg reflector ridge waveguide diode laser with wavelength close to 1120 nm. Picosecond optical pulses were generated by gain-switching at variable repetition frequencies up to 80 MHz. In single-pulse operation, a pulse width of 92 ps with a pulse peak power of 1.7 W at 10 MHz could be obtained. Investigations in operation at higher injection current pulse amplitude increased the pulse peak power to 2.6 W, but also showed significant trailing pulses which is typical for gain-switched diode lasers. The shape of the pulses is stable over the whole range of the investigated repetition frequencies from 5 to 80 MHz. At an operation temperature of 25 °C, the emitted radiation has a wavelength of 1114.7 nm and increases to 1116.4 nm at 45 °C. The central wavelength does not change significantly at higher output power.

Innovative Laser Sources Operating Around 2 μm

We report on a variety of continuous wave and pulsed laser sources based on Thulium- and Holmium-doped materials, emitting in the spectral range around 2 μm. This includes continuous wave Thulium-doped fiber lasers which have been realized based on the beam combining technique by using tapered fused bundles and truly single mode WDM cascades, respectively. A pulsed laser source emitting nano- or picosecond pulses has been developed in a master oscillator power amplifier (MOPA) configuration, which consists of a gain-switched diode operating at a wavelength of 1.95 μm, followed by Thulium-doped fiber-based pre- and main amplifiers. Furthermore, we present a femtosecond regenerative amplifier system using Thulium:YAP and Holmium:YAG crystals with emission wavelengths around 1.95 μm and 2.1 μm, respectively. Output energies of more than 700 μJ have been generated with both systems.

Investigation of a versatile pulsed laser source based on a diode seed and ultra-high gain bounce geometry amplifiers.

We present an investigation of a versatile pulsed laser source using a low power, gain-switched diode laser with independently variable repetition rate and pulse duration to seed an ultra-high gain Nd:YVO4 bounce geometry amplifier system at 1064nm. Small-signal gain as high as 50dB was demonstrated in a bounce geometry pre-amplifier from just 24W pumping, with good preservation of TEM00 beam quality. The single amplifier is shown to be limited by amplified spontaneous emission. Study is made of further scaling with a second power amplifier, achieving average output power of ~14W for a pulsed diode seed input of 188μW. This investigation provides some guidelines for using the bounce amplifier to obtain flexible pulse amplification of low-power seed sources to reach scientifically and commercially useful power levels.

Compact high‐current diode laser nanosecond‐pulse source with high efficiency and 13 µJ output energy

A compact gain-switched nanosecond diode laser pulse source at 920 nm with an output energy of 13 µJ is presented. The developed nanosecond electronic driver is based on GaN transistors and controlled by transistor–transistor logic compatible input pulses. A peak current of more than 430 A for 20–50 ns-long pulses with a repetition rate up to 100 kHz and an electrical efficiency of more than 50% is reached. About 50 ns optical pulses with a peak power of 250 W (13 µJ) are generated with a tapered ridge waveguide bar with 29 emitters. The rise and fall time of the pulses is about 13 ns.

100 kW peak power picosecond thulium-doped fiber amplifier system seeded by a gain-switched diode laser at 2 μm

We report on the generation of picosecond pulses at 2 μm directly from a gain-switched discrete-mode diode laser and their amplification in a multistage thulium-doped fiber amplifier chain. The system is capable of operating at repetition rates in the range of 2 MHz-1.5 GHz without change of configuration, delivering high-quality 33 ps pulses with up to 3.5 μJ energy and 100 kW peak power, as well as up to 18 W of average power. These results represent a major technological advance and a 1 order of magnitude increase in peak power and pulse energy compared to existing picosecond sources at 2 μm.

High-power, variable repetition rate, picosecond optical parametric oscillator pumped by an amplified gain-switched diode

We demonstrate a picosecond optical parametric oscillator (OPO) that is synchronously pumped by a fiber-amplified gain-switched laser diode. At 24W of pump power, up to 7.3W at 1.54microm and 3.1W at 3.4microm is obtained in separate output beams. The periodically poled MgO-doped LiNbO(3) OPO operates with ~17ps pulses at a fundamental repetition rate of 114.8MHz but can be switched to higher repetition rates up to ~1GHz. Tunabilty between 1.4microm and 1.7microm (signal) and 2.9microm and 4.4microm (idler) is demonstrated by translating the nonlinear crystal to access different poling-period gratings and typical M(2) values of 1.1 by 1.2 (signal) and 1.6 by 3.2 (idler) are measured at high power for the singly resonant oscillator.

Full Characterization of Low-Power Picosecond Pulses From a Gain-Switched Diode Laser Using Electrooptic Modulation-Based Linear FROG

We use a linear frequency-resolved optical gating technique based on electrooptic modulation to fully characterize for the first time the highly chirped pulses from a 1.06-m Fabry-Perot laser diode and design a chirped fiber Bragg grating to provide high-quality pulse compression. With this grating, we achieved 18-ps pulses at a repetition rate of 1.35 GHz with a time-bandwidth product of 0.7.

Fiber-optic ring-down spectroscopy using a tunable picosecond gain-switched diode laser

Visible and near-infrared laser light pulses were coupled into two different types of optical fiber cavities. One cavity consisted of a short strand of fiber waveguide that contained two identical fiber Bragg gratings. Another cavity was made using a loop of optical fiber. In either cavity ∼40 ps laser pulses, which were generated using a custom-built gain-switched diode laser, circulated for a large number of round trips. The optical loss of either cavity was determined from the ring-down times. Cavity ring-down spectroscopy was performed on 200 pL volumes of liquid samples that were injected into the cavities using a 100 μm gap in the fiber loop. A detection limit of 20 ppm of methylene blue dye in aqueous solution, corresponding to a minimum absorptivity of εC<6 cm-1, was realized.

Synchronous photoinjection using a frequency-doubled gain-switched fiber-coupled seed laser and ErYb-doped fiber amplifier

Light at 1560 nm from a gain-switched fiber-coupled diode laser and ErYb-doped fiber amplifier was frequency doubled to obtain over 2 W average power at 780 nm with $\ensuremath{\sim}40\text{ }\text{ }\mathrm{ps}$ pulses and pulse repetition rate of 499 MHz. This light was used to drive the 100 kV DC high voltage GaAs photoemission gun at the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory to produce a high average current beam ($100\text{ }\text{ }\ensuremath{\mu}\mathrm{A}$) of highly spin-polarized electrons ($&gt;80%$). This new drive-laser system represents a significant advance over laser systems used previously, providing significantly higher power and enhanced reliability.

High average power, high repetition rate, picosecond pulsed fiber master oscillator power amplifier source seeded by a gain-switched laser diode at 1060 nm

We demonstrate a pulsed ytterbium-doped fiber master-oscillator power amplifier source at 1060 nm producing over 300 W of average power in 20-ps pulses at 1-GHz repetition rate. The pulses generated by a gain-switched diode were compressed by a chirped fiber Bragg grating and amplified without any distortion with excellent spectral quality. This fiber master oscillator power amplifier system offers versatility and potential for further power scaling.

Tunable and multiple-wavelengths/temporal output from gain-switched diode laser and a four Bragg-grating Fiber

We demonstrate spectral narrowing and selective tuning of the picosecond pulse outputs from an injection-seeded, gain-switched diode laser that is simultaneously coupled to four output fibers with different Bragg-grating resonators. A single-, dual-, and triple-wavelength and temporal pulse operation from all four outputs is presented.

Dramatic spectral narrowing and broadband tuning from a self‐injection‐seeded diode laser

AbstractWe demonstrate spectral narrowing with broadband tuning from a picosecond self‐injection‐seeded gain‐switched diode laser. A narrowband spectral output was continuously tunable over a range of 44 nm from 1.538 to 1.582 μm. We also observe a gain‐switched hybrid‐operation regime with elements of mode‐locking. Our numerical simulations exhibit good agreement with the experimental results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 150–152, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20235

Dual-wavelength optical-pulse source based on diode lasers for high-repetition-rate, narrow-bandwidth terahertz-wave generation

Synchronized dual-wavelength 1-MHz repetition-rate optical pulses were successfully generated by the combination of a gain-switched diode laser and a wavelength-tunable continuous-wave diode laser at 1.5 mum. The timing synchronization of dual-wavelength optical pulses was achieved with four-wave mixing by use of a highly nonlinear optical fiber. This optical pulse source was utilized for terahertz (THz)-wave differencefrequency generation by use of slanted periodically poled LiNbO3 (PPLN). We generated between 1.05 and 2.1 THz by use of the proper grating period of slanted PPLN with a 10-GHz bandwidth.

Broadband tuning and dual-spectral/temporal outputs from a nonresonantly injection-seeded diode laser

We demonstrate spectral narrowing and continuous broadband tuning of the picosecond pulse outputs from a nonresonantly injection-seeded, gain-switched diode laser that can be operated in dual spectral/temporal regimes. A single spectral output was continuously tunable over a range of 85 nm and in a dual-wavelength operation the outputs had spectral separations were adjustable from 3.5 to 53 nm.

Tunable operation of a gain-switched diode laser by nonresonant self-injection seeding

We report tunable operation of a gain-switched diode laser by nonresonant self-injection seeding from an uncoated glass slide used as an external cavity reflector. A spectral linewidth reduction from 11 to 0.05 nm has been achieved for picosecond pulses with little effect on other laser characteristics. Good agreement with numerical simulations based on a compound-cavity laser model is also reported.

Near-transform-limited picosecond pulses from a gain-switched InGaAs diode laser with fiber Bragg gratings

We have generated near-transform-limited picosecond pulses (ΔτΔν≈0.45) from a gain-switched diode laser using periodic and chirped fiber Bragg gratings. This configuration reduced the spectral bandwidth from 11 to 0.08 nm and the pulse duration was reduced, from 30 to &amp;lt;18 ps. Average and peak powers of 27 and 770 mW, respectively, were obtained.

Nonresonant self-injection seeding of a gain-switched diode laser

We demonstrate step-tunable single-mode operation of a gain-switched diode laser by nonresonant self-injection seeding from an uncoated glass slide used as an external cavity reflector. A spectral bandwidth reduction from 11 nm to 0.05 nm and wavelength tunability has been achieved for picosecond (near-transform-limited) pulses with little effect on other laser characteristics. Good agreement with numerical simulations based on a compound-cavity laser model is also reported.