High brightness edge-emitting laser diode with wavelength self-organization in ultra-broad emitting area.

We have proposed and experimentally demonstrated an efficient method for generating high power and brightness based on an ultra-broad area laser diode (UBALD). We have developed a single-emitter UBALD capable of self-organization multi-wavelength emissions for two stripe widths of 2 and 5 mm, respectively. The 2 mm UBALD delivers an output power of 55 W with a beam quality M2 of 1.3 × 25.3 and a brightness of 179 MW/(cm2·sr). The 5 mm UBALD produces an output power of 121 W with a beam quality M2 of 2.1 × 32.7 and a brightness of 192 MW/(cm2·sr). To the best of our knowledge, these results represent the highest output power and highest brightness ever achieved from a single edge-emitting LD emitter to date.

High power single-frequency 1112†nm laser by an insertable Nd:YAG/YAG bonded monolithic planar ring oscillator.

A high power single-frequency operation at 1112 nm with novel insertable monolithic planar ring oscillator based on a Nd:YAG/YAG bonded crystal is proposed. In a proof-of-principle experiment, a finely designed coating on the output surface is carried out to ensure single-wavelength oscillation at 1112 nm, together with a half-wave plate and a Tb3Ga5O12 crystal inserted in the open space of the bonded block to realize the unidirectional operation with power scalability. Consequently, the single-frequency laser delivers an output power of 3.9 W at 1112.3 nm with a slope efficiency of 58.6% and an optical-to-optical efficiency of 17.7%. The power fluctuation is measured to be within ± 0.26% over 20 min, and the laser linewidth is estimated to be 4.15 MHz (Δλ = 0.017 pm).

Primary aberration optimization for double-plane symmetric beam shaping systems using a pair of curved reference surfaces.

The geometric aberration of centered refracting double-plane symmetric optical systems (DPSOS) is investigated. For DPSOS with different defocus values in the tangential plane and the sagittal plane (astigmatic wavefront), a pair of curved reference surfaces which vanishes the quadratic terms of the optical path difference (OPD) between a general ray and a reference ray are deduced. With the curved reference surfaces, the primary (fourth-order) wave aberration function for DPSOS is calculated and analyzed, which can be used for beam shaping designs with astigmatic input wavefront, such as slab lasers and semiconductor lasers. Further, the proposed curved reference surfaces can be applied to analyze the aberrations of general DPSOS.

1.53 W all-solid-state nanosecond pulsed mid-infrared laser at 6.45 µm.

A compact and robust all-solid-state mid-infrared (MIR) laser at 6.45 µm with high average output power and near-Gaussian beam quality is demonstrated. A maximum output power of 1.53 W with a pulse width of approximately 42 ns at 10 kHz is achieved using a ZnGeP2 (ZGP) optical parametric oscillator (OPO). This is the highest average power at 6.45 µm of any all-solid-state laser to the best of our knowledge. The average beam quality factor is measured to be M2 = 1.19. Moreover, high output power stability is confirmed, with a power fluctuation of less than 1.35% rms over 2 h, and the laser can run efficiently for more than 500 h in total. Using this 6.45 µm pulse as a radiation source, ablation of animal brain tissue is tested. Furthermore, the collateral damage effect is theoretically analyzed for the first time, to the best of our knowledge, and the results indicate that this MIR laser has excellent ablation ability, making it a potential replacement for free electron lasers.

Compact integrated aberration-compensating module for a 9 kW Nd:YAG slab laser based on an off-axis stable-unstable resonator.

An integrated aberration-compensating module (IACM), consisting mainly of an adjustable slab-aberration compensator, a one-dimensional Shack-Hartmann wavefront sensor, and a data processor, which meet the urgent requirements of correcting the specific wavefront aberrations of a slab laser based on an off-axis stable-unstable resonator, is designed and experimentally demonstrated. Benefits include compactness, robustness, simplicity, automation, and cost-effectiveness. The particular wavefront aberrations of the 9 kW level quasi-continuous-wave Nd:YAG slab laser, which have characteristics of asymmetry, large amplitude and gradient, high spatial frequency, and low temporal frequency, were measured and theoretically analyzed. In the experiment, the wavefront aberrations of the slab laser were corrected by the IACM. At the average output power of 9 kW, the diffraction-limited factor ß was improved from 20.3 times diffraction limit (DL) to 3.6 times DL. The peak-to-valley and root-mean-square values of aberrations were reduced from 9.6 to 0.85 µm and from 2.86 to 0.18 µm within five iterations of the IACM, respectively. Moreover, The IACM is capable of maintaining the compensating surface figure after power-off.

QCW surface-pumped cryogenically cooled single-slab laser with 1 kW level at 946 nm.

We present a kilowatt-level quasi-continuous-wave (QCW) cryogenically cooled 946-nm slab laser oscillator for the first time, to the best of our knowledge. The laser system is based on a double-face-pumped large-size single-slab Nd:YAG design, delivering a record-high average power of 1.06 kW without additional amplification. This laser oscillator operates at repetition rate of 400 Hz with a pulse duration of 175 µs, resulting in a single pulse energy of 2.65 J. To the best of our knowledge, these results represent the highest output power and pulse energy for any all-solid-state 946-nm laser ever reported to date. Our scheme paves a new path for the development of the compact high-power solid-state 946-nm laser.

Simplified analytical method for an anamorphic refractive shaping system of laser beams with a large aspect ratio.

For reshaping aperture size and correcting low-order aberration of laser beams with large aspect ratios, a simplified analytical method is proposed to design an anamorphic refractive shaping system, which is composed of double-plane symmetric lenses. The simplified method enables performing a global study of aberrations via calculating the analytical primary wave aberration function under paraxial approximation. The aberration balance is analyzed with a three-lens laser collimating system and a compact four-lens laser expanding system. Lens bending and conic surfaces are introduced to decrease ray errors. Through the simplified analytical method, anamorphic refractive shaping systems for laser beams with large aspect ratios can be adequately analyzed and conveniently designed.

High-repetition-rate 100 W level sodium beacon laser for a multi-conjugate adaptive optics system.

A 100 W level kilohertz repetition-rate microsecond (µs)-pulse all-solid-state sodium beacon laser at 589 nm is demonstrated for the first time, to the best of our knowledge, via combining two independent µs-pulsed lasers. Each beamlet is generated by the sum-frequency mixing of pulsed 1064 and 1319 nm lasers in a lithium triborate (LBO) crystal, which operate at 500 Hz pulse repetition frequency with 61 W $p$p-polarized and 53 W $s$s-polarized output, respectively. An incoherent sequence combining technology of polarized laser beams is employed to add the two beamlets. The average power of the combined beam is up to 107.5 W with a combining efficiency of 94.3%. The combined beam has a 1 kHz repetition rate with ${\sim}{120}\;\unicode{x00B5} {\rm s}$∼120µs pulse duration and beam quality ${M^2} = {1.41}$M2=1.41. The central wavelength with a linewidth of ${\sim}{0.3}\;{\rm GHz}$∼0.3GHz is locked to a sodium ${{\rm D}_{2a}}$D2a absorption line. To the best of our knowledge, this is a record-high power operating at kilohertz for µs-pulsed solid-state sodium beacon lasers.

Watt level laser source for a polychromatic laser guide stars: double resonant fluorescence from 3S1/2-3P3/2-3D5/2 transition of sodium atoms.

The polychromatic laser guide star (PLGS) is one of the solutions proposed to measure the differential atmospheric tip-tilt. A watts-level microsecond pulse all solid state laser source with two wavelengths at 589 and 819.7 nm are developed to perform a proof-of-concept on-sky test for what is believed to be the first time. By sum-frequency of 1319 and 1064 nm, a 44 W maximum average output power at 589.159 nm is generated with the pulse width of ~90 µs at 500 Hz, the linewidth of 0.46 pm, and the beam quality of M2 = 1.50. Meanwhile, a 2.4 W average output power is achieved operating at 819.710 nm with the pulse width of ~25 µs at 500 Hz, the linewidth of 0.8 pm, and beam quality factor of M2 = 1.20, which is end-pumped by a frequency-doubled 1064 nm Nd:YAG laser. Moreover, double resonant fluorescence in sodium cell with two step excitation of sodium atom from 3S1/2 to 3D5/2 via 3P3/2 level is observed clearly by tuning the wavelength of 589 and 819.7 nm beams. In the proof-of-principle experiment, it is preliminarily verified that this laser system is expected to be applied to the sky experiment.

Pulse duration adjusted by changing the cavity length with a multi-pass cavity in a Q-switched Nd:YAG laser.

We report a compact, long nanosecond (ns) pulse duration stretched laser source by a multi-pass cavity (MPC). Based on the combination of the MPC and pump power, a high-power high beam quality 1064 nm Q-switched Nd:YAG laser with a pulse duration adjustable over the range of 160-1000 ns was obtained at a pulse repetition frequency of 10 kHz for the first time, to the best of our knowledge. At a typical pulse width of 560 ns, an average output power of 10.6 W was successfully achieved. The beam quality factor M2 was measured to be 1.45 with a good Gaussian mode.

Picosecond slab regenerative amplifier using a large fundamental mode stable-unstable hybrid cavity.

Slab gain media with large aspect ratios were difficult to be adopted in ultrafast regenerative amplifiers (RAs) due to the obstacle of mode matching with the seed beam. We proposed that an unstable cavity could be employed to solve this difficulty by taking the advantage of its large fundamental mode volume. In this way, an Nd:YVO4 slab-based picosecond RA has been successfully demonstrated using a stable-unstable hybrid cavity. The maximum average output power of 10.5 W was achieved at the repetition rate of 10 kHz. The beam quality factor M2 was measured to be 1.54 in the stable direction and 2.26 in the unstable direction.

Dual-wavelength TEM01 mode passively mode-locked Nd:YAG laser witha semiconductor saturable absorber mirror.

A dual-wavelength ${{\rm TEM}_{01}}$TEM01 mode synchronous continuous wave passively mode-locked (CWML) Nd:YAG laser has been demonstrated for the first time to the best of our knowledge with a semiconductor saturable absorber mirror (SESAM) at 1319 and 1338 nm. The maximum average output power of 10.84 W was obtained at a 113.8 W absorbed pump power, corresponding to an optical-to-optical conversion efficiency of 9.5%. The dual-wavelength CWML pulses had a pulse duration of 35.1 ps at a repetition rate of 76 MHz. The beam quality was measured to be ${{\rm M}^2} = {2.51}$M2=2.51.

30.5-µJ, 10-kHz, picosecond optical parametric oscillator pumped synchronously and intracavity by a regenerative amplifier.

We have proposed a novel approach to realize a high-energy ultrafast optical parametric oscillator (OPO) by intracavity pumping in a regenerative amplifier. In this way, we have experimentally demonstrated an unprecedented pulse energy of 30.5 µJ from a 1.5-µm singly resonant synchronously pumped OPO at a pulse repetition rate of 10 kHz with a pulse width of 7.0 ps. To the best of our knowledge, this is the highest pulse energy from an ultrafast laser OPO.

High-energy single-frequency 167 nm deep-ultraviolet laser.

We report a high-energy single-frequency deep-ultraviolet (DUV) solid-state laser at 167.079 nm by the eighth-harmonic generation of a diode-pumped Nd:LGGG laser. A maximum DUV laser output energy of 1.5 µJ at a 5 Hz repetition rate with a 200 µs pulse duration is achieved. The central wavelength of the DUV laser is located at 167.079 nm and can be finely tuned from 167.075 to 167.083 nm. The linewidth is estimated to be 0.025 pm. To the best of our knowledge, this is the first Letter reporting a high-energy single-frequency solid-state DUV laser below 170 nm. The successful demonstration of the high-energy single-frequency DUV laser source with the unique wavelength is useful for direct detection of a Al+27 ion via resonance fluorescence in a multi-ion optical clock.

Picosecond mid-infrared optical parametric amplifier based on LiInSe2 with tenability extending from 3.6 to 4.8 µm.

A picosecond (ps) mid-infrared (MIR) optical parametric amplifier (OPA) with LiInSe2 crystal was demonstrated for the first time. The MIR OPA was pumped by a 30 ps 1064 nm Nd:YAG laser and injected by a barium boron oxide (BBO)-based widely tunable near-infrared seed. A maximum idler pulse energy of 433 µJ at 4 µm has been obtained under a pump energy of 17 mJ, and the corresponding pulse duration was estimated to be ~13 ps. To our knowledge, this is the highest single pulse energy generated by LiInSe2 crystal. Furthermore, an idler spectrum tuning from 3.6 to 4.8 µm was investigated at fixed pump energy of 15 mJ.

Pulse width adjustable Q-switched cavity dumped laser by rotating a quarter-wave plate and a Pockels cell.

A pulse width adjustable 1064 nm Q-switched cavity dumped Nd:YVO4 laser was realized for the first time, to the best of our knowledge, by rotating an intracavity quarter-wave plate (QWP) and a Pockels cell (PC). The pulse width adjustment range was 4.8-7.8 ns with a constant output power of 3.6 W, and it reached 4.8-13.5 ns for a lower output power of 1.3 W. The pulse width was dependent mostly on the rotating angle of the QWP and PC, but independent of the gain and pulse repetition rate.

Compact, high-power, high-beam-quality quasi-CW microsecond five-pass zigzag slab 1319 nm amplifier.

We demonstrate a compact, high-power, quasi-continuous-wave (QCW) end-pumped 1319 nm Nd:YAG slab amplifier laser with good beam quality. The laser is based on a QCW pulse Nd:YAG master oscillator and Nd:YAG slab amplifier with multi-pass zigzag architecture. The amplifier operates at a pulse repetition frequency of 500 Hz and pulse width of ∼105 µs, delivering a maximum output power of 51.5 W under absorbed pump power of 217.8 W and corresponding to an extraction efficiency of 14.2%. The beam quality factor is measured to be Mx2=1.61 and My2=1.81 in the orthogonal directions. To the best of our knowledge, this is the first compact, high-power, high-beam-quality QCW Nd:YAG amplifier at 1319 nm based on a multi-pass zigzag slab structure.

High-power QCW microsecond-pulse solid-state sodium beacon laser with spiking suppression and D2b re-pumping.

A 65 W quasi-continuous-wave microsecond-pulse solid-state sodium beacon laser tuned to the sodium D2a line has been developed with a linewidth of 0.3 GHz, beam quality of M2=1.38, and pulse width of 120 µs at a repetition rate of 500 Hz by sum-frequency mixing 1319 and 1064 nm diode-pumped Nd:YAG master-oscillator power-amplifier systems. The laser wavelength stability is less than ±0.15 GHz through feedback controlling. The laser spiking due to relaxation oscillations is suppressed by inserting frequency doublers in both 1319 and 1064 nm oscillators. Sodium D2b re-pumping is accomplished by tuning the frequency of the electro-optic modulator with the right D2a-D2b offset. A bright sodium laser guide star with a photon return of 1820 photons/cm2/s was achieved with the laser system when a 32 W circular polarized beam was projected to the sky during our field test at the Xinglong Observatory.

Sub-pm linewidth nanosecond Nd:GYSGG laser at 1336.6 nm.

We demonstrate a sub-pm linewidth acousto-optic (AO) Q-switched nanosecond Nd:GYSGG ring laser at 1336.6 nm side-pumped by 808-nm quasi-continuous wave (QCW) diode lasers for the first time. With incident pulse energy of 4.23 J at 10 Hz, a maximum output macropulse energy of 36.7 mJ at 1336.6 nm with linewidth of less than 0.85 pm and a micropulse width of 300 ns was obtained at a repetition rate of 80 Hz, corresponding to an average micropulse peak power of 15.3 kW. The M² factors were measured to be 1.42 and 1.10 in x and y directions, respectively. It can be tuned from 1336.576 to 1336.652 nm with a tuning resolution of 1 pm. The 1336.632 nm can be converted to deep ultraviolet (DUV) laser at 167.079 nm through its eighth harmonics, which is very useful for the ²7Al⁺ optical frequency standard.

167.75-nm vacuum-ultraviolet ps laser by eighth-harmonic generation of a 1342-nm Nd:YVO4 amplifier in KBBF.

We demonstrate a ps 167.75-nm vacuum-ultraviolet (VUV) laser by cascaded second-harmonic generation (SHG). The VUV laser is produced by eighth-harmonic generation (EHG) of a mode-locked ps 1342-nm Nd:YVO4 amplifier through three stages cascaded SHG with two LiB3O5 crystals and one KBe2BO3F2 crystal, successively. The 167.75-nm laser provides up to 65-µW output power, and the corresponding photon flux and photon flux density are 5.5×10(13) s(-1) and 1.6×10(18) s(-1)·cm(-2), respectively.