YAG Nonplanar Ring Oscillator Research Articles

1645-nm single-frequency vortex laser from an Er:YAG nonplanar ring oscillator.

A 1645-nm single-frequency vortex beam with narrow linewidth from an Er:YAG nonplanar ring oscillator (NPRO) using an annular pump beam is demonstrated. The pump beam from a 1532-nm fiber laser is shaped to an annular beam by an axicon. The Er:YAG NPRO generates a 1.96-W single-frequency vortex beam under a pump power of 13 W. The linewidth of the 1645-nm vortex laser is measured as 6 kHz. This work provides a convenient way of single-frequency vortex beam generation.

High-repetition-rate single-frequency Ho:YAG MOPA system.

A stable, 2.09μm single-frequency Ho:YAG master oscillator and power amplifier (MOPA) system at a pulse repetition frequency of 1.25kHz is demonstrated. The maximum output energy of the single-frequency injection-seeded laser is 13.76mJ, and the corresponding pulse width is 178.9ns. The seed laser is a continuous-wave Ho:YAG non-planar ring oscillator laser. The half-width of the pulse spectrum is measured to be 2.65MHz by using the heterodyne technique, which is about 1.06 times Fourier transform limited.

1 kHz single-frequency 2.09 μm Ho:YAG ring laser.

In this paper, we report the experimental realization of a high-repetition-rate single-frequency Ho-doped yttrium aluminum garnet (Ho:YAG) ring laser at 2.09μm. Single-frequency operation of the ring laser is achieved by injection-seeding with a continuous wave (CW) Ho:YAG non-planar ring oscillator (NPRO) laser. The output energy of the ring laser is 6.24mJ with a pulse width of 172ns and a repetition rate of 1kHz. The beam quality M2-factor is measured to be ∼1.3 at the maximum output energy. The half-width of the pulse spectrum is measured to be 2.61MHz by a heterodyne technique.

Single-frequency injection-seeded Q-switched Ho:YAG laser

An injection-seeded Ho:YAG laser at 2090 nm with changeable pulse repetition frequency (PRF) is demonstrated. Containing a Ho:YAG nonplanar ring oscillator (NPRO) seed, a slave laser, and a single-pass amplifier, the laser delivered single-frequency pulses with energy ranging from 31.4 to 12.7 mJ. The corresponding pulse duration and PRF varied between 102–215 ns and 150–750 Hz, respectively. To the best of our knowledge, this is the highest PRF ever obtained from a single-frequency Ho:YAG laser.

Kerr-lens mode-locked polycrystalline Cr:ZnS femtosecond laser pumped by a monolithic Er:YAG laser**Project supported by the National Natural Science Foundation of China (Grant Nos. 61205130, 61465012, and 61564008).

We demonstrated a Kerr-lens mode-locked polycrystalline Cr:ZnS laser pumped by a narrow-linewidth linear-polarised monolithic Er:YAG nonplanar ring oscillator operated at 1645 nm. With a 5-mm-thick sapphire plate for intracavity dispersion compensation, a compact and stable Kerr-lens mode-locking operation was realised. The oscillator delivered 125-fs pulses at 2347 nm with an average power of 80 mW. Owing to the special polycrystalline structure of the Cr:ZnS crystal, the second to fourth harmonic generation was observed by random quasi-phase-matching.

15 mJ single-frequency Ho:YAG laser resonantly pumped by a 1.9 µm laser diode

A 2.09 µm injection-seeded single-frequency Ho:YAG laser resonantly pumped by a 1.91 µm laser diode is demonstrated for the first time. The seed laser is a continuous wave (CW) Ho:YAG non-planar ring oscillator. 15.15 mJ single-frequency output energy is obtained from the injection-seeded Q-switched Ho:YAG laser, with a pulse repetition rate of 200 Hz and a pulse width of 109 ns. The half-width of the pulse spectrum is measured to be 4.19 MHz by using the heterodyne technique. The fluctuation of the center frequency of the single-frequency pulses is 1.52 MHz (root mean square (RMS)) in 1 h.

Characteristics and performance of offset phase locked single frequency heterodyned laser systems

We demonstrate and characterize the performance of two heterodyned optical phase locked loop (PLL) laser systems for use in characterizing photodetector RF frequency response and nonlinearities. Descriptions of PLL circuit parameters for Nd:YAG non-planar ring oscillator lasers at 1064 nm and 1319 nm, and Er ion fiber lasers from 1530 nm to 1565 nm are presented. Both laser systems have piezoelectric transducer wavelength control over the PLL voltage controlled oscillator circuit. Offset frequency phase locking from 1.5 kHz to 51+ GHz is demonstrated. Frequency stability at 10 MHz is measured to be ±50 μHz, limited by the stability of the Rb stabilized crystal oscillator. Phase noise of the phase-locked 1319 nm laser system is discussed where we find that the phase noise is dominated by the input source noise at frequency offsets below 100 Hz and by the laser's RIN noise at frequency offsets > 100 Hz. Comparing nonlinearity data from an InGaAs p-i-n photodiode using both 1319 nm and 1550 nm PLL nonlinearity measurement systems, we find two new separate photodetector nonlinearity mechanisms. Measurements of the harmonic components of a 11 MHz sinusoidal heterodyned optical beat note signal are found to be at or below 1 nW/mW for the second harmonic (at 22 MHz) and at or below 0.25 nW/mW for the 3rd harmonic (at 33 MHz), confirming the nearly pure sinusoidal nature of the optically generated microwave beat note.

50 W low noise dual-frequency laser fiber power amplifier.

A three-stage dual-frequency laser signal amplification system is presented. An output from a narrow-linewidth Nd:YAG nonplanar ring-oscillator (NPRO) is split into two parts, one of them is frequency shifted by an acoustooptic modulator (AOM) then coupled into a single mode optical fiber. The other part is coupled into another single mode fiber then combined with the frequency-shifted beam with a 2 to 1 single mode fiber coupler. The combined beam has a power of 20 mW containing two frequency components with frequency separation of 150 ± 25 MHz. The dual-frequency signal is amplified via a three-stage Yb3+-doped diode pumped fiber power amplifier. The maximum amplified power is 50.3 W corresponding to a slope efficiency of 73.72% of the last stage. The modulation depth and signal to noise ratio (SNR) of the beat signal are well maintained in the amplifying process. The dual-frequency laser fiber power amplifier provides robust optical carried RF signal with high power and low noise.

A high-finesse Fabry–Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

A high-finesse Fabry–Perot cavity with a frequency-doubled continuous wave green laser (532nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO3 crystal. The maximum achieved green power at 5W infrared pump power is 1.74W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.06GeV and 50μA.

Single-frequency, Q -switched Er:YAG at room temperature injection-seeded by an Er:YAG nonplanar ring oscillator

We demonstrate a diode-pumped, injection-seeded Q-switched Er:YAG laser operating at room temperature. The diode-pumped single-frequency Er:YAG monolithic nonplanar ring oscillator (NPRO) was used as the seed laser emitting at 1645.22 nm with a maximum output power of 550 mW. Single-frequency, Q-switched operation of the Er:YAG laser was achieved by injection seeding. The output energy of the single-frequency Q-switched pulse was 3.5 mJ, with a pulse width of 195 ns at a repetition rate of 100 Hz.

Passively Q-switched single-frequency output from a diffusion-bonded monolithic Nd:YAG non-planar ring oscillator

A compact monolithic Nd:YAG non-planar ring laser with diffusion-bonded Cr4+:YAG is demonstrated, and high stable pulsed single-frequency laser at 1.06 \mu m is realized. Theoretical analysis and simulation results of pulsed laser parameters are illustrated. 14.96-kW maximum peak power, pulse-width of 4.8 ns is achieved for single-frequency operation.

Single-frequency and dual-wavelength Ho:YAG nonplanar ring oscillator resonantly pumped by a Tm:YLF laser

A resonantly pumped monolithic Ho:YAG nonplanar ring oscillator (NPRO) with single-frequency and dual-wavelength laser outputs is demonstrated. The Ho:YAG NPRO is resonantly pumped by a 1907-nm Tm:YLF laser. In single-frequency operation, the output power is 3.09 W, with a slope efficiency of 61% and an optical efficiency of 48% with respect to the pump power. Up to 10 W dual-wavelength laser output at 2091 and 2097 nm is also obtained from the Ho:YAG NPRO with the maximum pump power, with a slope efficiency of 61% with respect to the pump power.

A Resonantly Pumped 1645 nm Er:YAG Nonplanar Ring Oscillator With 10.5 W Single Frequency Output

We demonstrate a single frequency Er:YAG nonplanar ring oscillator (NPRO) resonantly pumped by a fiber laser. Up to 10.5 W single frequency laser output with a slope efficiency of 60.03% was achieved by optimizing the parameters of the Er:YAG NPRO. At 10.5 W output power the $M^{2}$ -factors of the Er:YAG NPRO were 1.09 and 1.24 in the $x$ - and $y$ - directions, respectively. The linewidth of the Er:YAG NPRO was 18.6 kHz.

Room temperature single longitudinal mode laser output at 1645 nm from a laser-diode pumped Er:YAG nonplanar ring oscillator

We report on a monolithic 1645 nm Er:YAG nonplanar ring oscillator (NPRO) resonantly pumped by a fiber-coupled laser diode. In the experiment, an up to 550 mW single frequency laser output at 1645.2 nm was obtained, corresponding to a slope efficiency of 19.1% and an absolute efficiency of 6.0%. The beam quality M2 was measured to be 2.1 at the highest output power.

Single frequency 1645 nm Er:YAG nonplanar ring oscillator resonantly pumped by a 1470 nm laser diode

A 1645 nm Er:YAG nonplanar ring oscillator, resonantly pumped by a 1470 nm laser diode, is reported. By using a 0.5%-doped Er:YAG nonplanar ring resonator, a 0.284 W single-frequency laser output at 1645 nm was obtained with a slope efficiency of 42.1%. The beam quality in x and y directions were 1.064 and 1.039, respectively.

61 W single frequency laser output at 1645 nm from a resonantly pumped Er:YAG nonplanar ring oscillator

A monolithic 1645 nm Er:YAG nonplanar ring oscillator (NPRO) resonantly pumped by a 1532 nm fiber laser is demonstrated. For reducing the energy-transfer upconversion effect, a 0.5% doped Er:YAG nonplanar crystal was used. An up to 6.1 W single frequency laser output at 1645 nm was obtained, with a slope efficiency of 55.2% and an optical efficiency of 48.0%. The linewidth of the Er:YAG NPRO was 14.4 kHz.

Narrowband Er:YAG nonplanar ring oscillator at 1645 nm

We report 1645 nm narrowband operation of a monolithic Er:YAG nonplanar ring oscillator resonantly pumped at 1532 nm. Unidirectional cw power up to 0.5 W was obtained with a measured linewidth of 21 kHz.

Single-frequency operation of diode-pumped 2 μm Q-switched Tm:YAG laser injection seeded by monolithic nonplanar ring laser

We present a diode-pumped, 2mum single-frequency Q-switched Tm:YAG laser. The Q-switched laser is injection seeded by a monolithic Tm:YAG nonplanar ring oscillator with the ramp-hold-fire technique. The output energy of the 2mum single-frequency Q-switched pulse is 2.23mJ, with a pulse width of 290ns and a repetition rate of 200Hz. From the heterodyne beating measurement, the frequency difference between the seed laser and the Q-switched laser is determined to be 37.66MHz, with a half-width of the symmetric spectrum of about 2 MHz.

Diode-pumped single-frequency Tm:YAG NPRO laser by using different pumping spot sizes

This paper presents the experimental results of the monolithic Tm:YAG nonplanar ring oscillator (NPRO) pumped by two kinds of laser diodes with different pumping spot sizes. By longitudinal pumping in continuous-wave operation, a single-frequency output power of 404 mW was obtained at room temperature, with a slope efficiency of 48.2%. The influences of the pumping spot sizes on the beam properties were also discussed.

Stable single-frequency output at 201 μm from a diode-pumped monolithic double diffusion-bonded Tm:YAG nonplanar ring oscillator at room temperature

We demonstrate a monolithic double diffusion-bonded monolithic Tm:YAG nonplanar ring laser pumped by a fiber-coupled laser diode. Up to 867 mW single-frequency output at 2.01 microm was obtained from the Tm:YAG system at room temperature, with a slope efficiency and an optical-optical efficiency of 31.6% and 19.2%. The power stability of the single frequency laser was 0.32% within 30 min.