Single-frequency Tm Research Articles

Efficient single-frequency Tm:YAG crystal-derived silica fiber laser at 1.7 µm.

A single-frequency distributed Bragg reflector (DBR) fiber laser operating at 1720 nm has been demonstrated for the first time using a Tm:YAG crystal-derived silica fiber (TCDSF), to the best of our knowledge. A single-frequency laser with an over 220 mW output power was achieved from a 1.5-cm-long TCDSF when being in-band pumped by a homemade 1610 nm fiber laser. The slope efficiency reached 25.30% for the absorbed pump power. The optical signal-to-noise ratio (OSNR) of the laser was ∼69.78 dB, and the laser linewidth was ∼84.5 kHz. Additionally, the measured relative intensity noise (RIN) remained at -130 dB/Hz at frequencies above 9 MHz. The experimental results indicate that the TCDSF is a promising gain medium for single-frequency lasers at 1.7 µm.

Dual-wavelength single-frequency Tm:ZBLAN fiber amplifier operating at 1.94 and 2.33 μm

We report here, to the best of our knowledge, the first dual-wavelength single-frequency thulium-doped fiber amplifier operating at 1.94 and 2.33 μm. The single-stage, Tm3+-doped ZBLAN fiber amplifier, ground-state pumped by a 793-nm laser diode, yielded a stable output power of 1.45 W at 2332 nm and 7.4 W at 1939 nm. The injection of 1.94-μm seed effectively suppresses parasitic lasing in the 2.33-μm Tm fiber amplifier. The experiment investigated the competitive relationship between the 2-μm transition and the 2.3-μm transition, and the results suggest that the injection of 1.94-μm seeds is beneficial to the improvement of 2.33-μm efficiency, while the injection of 2.33-μm seed slightly reduces the 1.94-μm efficiency.

2.3-µm single-frequency Tm: ZBLAN fiber amplifier with output power of 1.41 W.

We present here the first watt-level single-frequency thulium-doped ZBLAN fiber amplifier system operating at a wavelength of 2.3 µm. Continuous-wave output of up to 1.41 W was generated from a two-stage Tm: ZBLAN fiber amplifier with direct ground-state pumping at 793 nm. Seeded by a single-frequency distributed feedback diode laser at 2332 nm, the thulium-doped ZBLAN fiber amplifier emitted a laser with linewidth no more than 10 MHz at maximal output power. This study examines the impact of a 2.3-µm seed on the competitive laser transition of 2 µm. The findings indicate that direct pumping of a Tm fiber amplifier holds the potential for achieving higher power output within the 2.3-µm band.

Double Fabry–Pérot etalons assistant injection-seeded single-frequency Tm,Ho:YLF laser

In this paper, we report a diode side-pumped injection-seeded single-frequency Tm,Ho:YLF laser, which operated at lasing threshold and emitted at 2051.2 nm. The assistance of Fabry–Pérot (FP) etalons to seed injection via mode selection was investigated. An acousto-optic Q-switched output of 6.7 mJ was achieved at 5 Hz. A temporal pulse duration of 310 ns with spectral linewidth of 2.0 MHz and frequency stability of 0.8 MHz root-mean-square (rms) was detected. The beam profile was a high-quality Gaussian TEM00 mode with M2x/y of ~ 1.15/1.14. This 2 μm laser source would be a good candidate for ground-based wind-detection coherent Lidar system.

High Power Single Frequency Tm:Y2O3 Ceramic Laser at 2015 nm

We report on high power, single-frequency operation of a compact Tm:Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic laser in 2 μm spectral region employing a volume Bragg grating in a simple linear resonator to serve simultaneously as a resonator mirror and mode selector. The home developed laser quality Tm:Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic sample has a Tm doped concentration of 2 at.% and pumped with a fiber coupled 793 nm laser diode. Up to 1.5 W of CW single frequency output power at 2014.9 nm has been generated, corresponding to a slope efficiency of 37.9% with respect to absorbed pump power. M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> factor of the output beam was measured to be ∼1.03.

2-μm double-pulse single-frequency Tm:fiber laser pumped Ho:YLF laser for a space-borne CO2 lidar.

In the framework of space-borne CO2 lidar development, the transmitter is a critical unit. We report on the development and the assessment of performances of a 2-μm single-frequency thulium fiber laser pumped Q-switched Ho:YLF laser. To fulfill the requirements of space-based operation, a master oscillator power amplifier architecture has been chosen, and the oscillator works in double-pulse operation. The transmitter can generate a single-mode dual wavelength emission "ON" and "OFF" around the R30e line of the 20013←00001 band of CO212. It delivers a pair of OFF-ON pulses with 12mJ and 42mJ energy, respectively, at a pulse repetition frequency of 303.5Hz. The pulse energy and central frequency stabilities are especially documented as well as pulse duration, polarization, overall efficiency, beam quality, pointing stability, and spectral purity. The possible limitations by light-induced damage or radiation-induced attenuation on the laser performances are also evaluated.

Longwave infrared, single-frequency, tunable, pulsed optical parametric oscillator based on orientation-patterned GaAs for gas sensing.

We demonstrate a nanosecond single-frequency nested cavity optical parametric oscillator (NesCOPO) based on orientation-patterned GaAs (OP-GaAs). Its low threshold energy of 10 μJ enables to pump it with a pulsed single-frequency Tm:YAP microlaser. Stable single-longitudinal-mode emission is obtained owing to Vernier spectral filtering provided by the dual-cavity doubly-resonant NesCOPO scheme. Crystal temperature tuning covers the 10.3-10.9 μm range with a quasi-phase-matching period of 72.6 μm. A first step toward the implementation of this device in a differential absorption lidar is demonstrated by carrying out short-range standoff detection of ammonia vapor around 10.4 μm. Owing to the single-frequency emission, interferences due to absorption by atmospheric water vapor can be discriminated from the analyte signal.

Diode-end-pumped continuously tunable single frequency Tm, Ho:LLF laser at 206 μm

We report on a laser diode-end-pumped continuously tunable single frequency Tm, Ho:LLF laser near room temperature. For transmission of 5%, the maximum single frequency output power of 221 mW at 2064.4 nm was obtained by using two uncoated etalons. The single frequency Tm, Ho:LLF laser operated on the fundamental transverse mode with an M2 factor of 1.13, and the output frequency could be tuned continuously near 1.5 GHz by angle tuning only of the 1 mm thick etalon. Furthermore, the influence of output coupler transmission on the laser performance was also investigated. The single frequency laser can be used as a seed laser for coherent Doppler lidar and differential absorption lidar systems.

Single-clad Tm–Ho:fiber amplifier for high-power sub-100-fs pulses around 19 μm

A Tm-Ho:fiber amplifier based on single-clad geometry is demonstrated for the generation of high-power femtosecond pulses around 1.9 μm. The amplifier is seeded by the low-power Raman soliton generated by an Er:fiber femtosecond laser. Pulse trains at a repetition rate of 250 MHz tunable from 1.84 to 1.92 μm with corresponding powers from 2.6 to 3 W and durations from 80 to 105 fs have been obtained. Beating with a single-frequency Tm laser has shown that the pulse coherence is highly preserved. The overall power fluctuations have been measured to be as low as 0.6%.

A single longitudinal mode Tm, Ho:YLF laser with a continuously tunable frequency of 2.1 GHz with double F–P etalons

A diode-end-pumped single-frequency Tm (5%), Ho (0.5%):YLF laser is reported. At room temperature, the maximum single longitudinal mode (SLM) output power of 83 mW at a wavelength of 2068.7 nm was obtained, corresponding to a slope efficiency of 5.57%. The beam quality M2 of 1.73 was measured at the maximum single-frequency output power. The output frequency of the SLM Tm, Ho:YLF laser can be tuned continuously over 2.1 GHz.

Compact single-frequency Tm:YAG ceramic laser with a volume Bragg grating

We demonstrated a compact high-power single-frequency Tm:YAG ceramic laser operating at 1999.7 nm. Single-frequency operation was achieved by incorporating a reflection volume Bragg grating (VBG) in a laser with a short cavity length. The laser emission has a spectral linewidth of ∼10 MHz and a maximum output power of 1.4 W, which is limited by the pump-induced thermal-lens effect of the laser.

Diode-pumped 2 μm tunable single-frequency Tm:LuAG laser with intracavity etalons

We report a laser-diode-pumped 2 μm single-frequency Tm:LuAG laser at room temperature. Two fused-silica etalons were used as mode selectors for the single-frequency operation. The maximum single-frequency output power was 616 mW at wavelength of 2021 nm, with a relative power stability of 0.61%. The wavelength tuning range of the single-frequency Tm:LuAG laser was 11 nm from 2018.714 to 2029.876 nm. The M(2) factors were measured to be 1.38 and 1.36 in the x and y directions, respectively.

Room Temperature Diode-Pumped Tunable Single-Frequency Tm:YAG Ceramic Laser

A single-longitudinal-mode (SLM) Tm:YAG ceramic laser under room temperature conditions using double Fabry—Pérot etalons is investigated. The maximum single-frequency output power is 318 mW with a slope efficiency of 12.6%. The wavelength tuning range from 2005nm to 2029nm is achieved by tuning the obliquity of a 0.1-mm-thick etalon. The single frequency laser has a beam quality of M2 = 1.3 at the maximum single-frequency output power. The result is reported for the first time to the best of our knowledge. This SLM Tm:YAG ceramic laser can replace the Tm:YAG single crystal laser to be used as the seed laser for LIDAR laser systems.

Single-frequency, Q-switched Ho:YAG laser at room temperature injection-seeded by two F–P etalons-restricted Tm, Ho:YAG laser

We demonstrated a 1.91 μm pumped, injection-seeded Q-switched Ho:YAG laser operating at room temperature. By inserting two Fabry-Perot etalons into the laser cavity, single-frequency Tm, Ho:YAG seed lasing was achieved at a wavelength of 2090.9 nm, with a typical output power of 60 mW. Single-frequency, nearly transform-limited Q-switched operation of the Ho:YAG laser was achieved by injection seeding. The output energy of the single-frequency Q-switched pulse is 7.6 mJ, with a pulse width of 132 ns and a repetition rate of 100 Hz. We measured the pulse spectrum, half-width of which was 3.5 MHz, by a heterodyne technique.

Room temperature diode-pumped Tm:YAG laser at 2008 nm

A diode end-pumped single-frequency Tm:YAG laser at room temperature was reported. The maximal output power of single-frequency is 30 mW by using two uncoated etalons. We obtained a single frequency Tm:YAG laser at 2008.14 nm. The single-longitudinal-mode laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.

Room temperature diode-pumped 1875.1 nm Tm:GdVO4 laser

A diode end-pumped single-frequency Tm:GdVO4 laser at room temperature was reported. The maximal output power of single-frequency is as high as 66 mW by using two uncoated fused etalons, which are respectively 0.05 mm thick YAG and 1 mm thick quartz. We obtained the single frequency Tm:GdVO4 laser at 1875.1 nm. The slope efficiency is 1.5%. The change of the lasing wavelength on temperature was also measured. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.

2 μm single-frequency Tm:YAG laser generated from a diode-pumped L-shaped twisted mode cavity

A 2 μm single-frequency Tm:YAG laser was developed by using a diode pumped L-shaped twisted-mode-cavity. By suppressing the spatial hole-burning, the 2 μm single-frequency laser was obtained, with the output power of 1.46 W and the slope efficiency of 19.2%.

A diode-pumped tunable single frequency Tm:YAG laser at room temperature using two etalons

We report a diode pumped single frequency Tm:YAG laser with two coated fused silica etalons as mode selectors. The maximum single frequency output power was 681 mW with the pumping power of 4.83 W. The slope efficiency of single-frequency laser was 20.5% and the optical-to-optical conversion efficiency was 14.2%. According to the experimental results, we developed a prototype with the maximum single frequency output power of 249 mW and the slope efficiency of 23.1%. The frequency tuning was investigated by changing the temperature of the crystal. A tuning coefficient of 2.57 GHz/°C was obtained. The beam propagation factors M2 were measured as 1.01 in both directions. The linewidth of the single frequency was 40 kHz.

Room temperature single-frequency output at 2118 nm from a diode-pumped Tm, Ho:YAP laser

A diode end-pumped single-frequency Tm, Ho:YAP laser at room temperature was reported. We demonstrated a single-frequency Tm, Ho:YAP laser at 2118.09 nm wavelength with output power up to 57 mW using two Fabry-Perot intracavity etalons. The optical conversion efficiency is 2.0% and the slope efficiency is 12.7%. The measured full width at half maximum linewidth was <7.5 pm limited by the resolution of the scanning Fabry-Perot etalon used to make the measurement. The wavelength was demonstrated to be stable to about 2 pm over 40 s time periods limited by the temperature stability of the laser. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.

Diode-pumped single-frequency Tm:GdVO4 laser at 1897.6 nm

A diode end-pumped Tm:GdVO4 laser at room temperature is reported. The maximal output power of single-frequency is as high as 34 mW by using two uncoated fused etalons, which are respectively 0.05 mm thick YAG and 1mm thick quartz. We obtained the single frequency Tm:GdVO4 laser at 1897.6 nm with the slope efficiency of 1.3%. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.