Walk-off Compensation Research Articles

Cascade picosecond optical parametric amplification for generating radiation in the 2.1 [formula omitted

The paper demonstrates the experimental implementation of a broadband picosecond radiation source with a wavelength of 2.0−2.2μm based on a cascade parametric amplifier. To do this, in the first cascade, as a result of parametric luminescence in the MgO:PPLN fan-out crystal, pumped by Nd:YAG laser pulses (90 ps, 10 Hz), radiation with a wavelength of 2.1μm and a pulse energy of ∼185 μJ at a pump energy of 6.5 mJ was generated. To increase the output radiation energy to a level of ∼840 μJ, a second parametric amplification cascade based on two KTiOPO4 crystals with a walk-off angle compensation was used. The results of numerical simulation of the spatial and energy characteristics of the radiation being generated are in good agreement with the experimental results. The developed picosecond 2.1μm radiation source is designed to be used for mid-IR range supercontinuum generation in non-oxide crystals.

Optimal design for wavelength conversion with a configuration of walk-off compensation in free space in the nanosecond pulsed regime

On the basis of standard wavelength conversion by the use of angular phase matching of nonlinear optical crystals arranged in free space, applicable to a wide range of wavelengths and laser intensities, we both numerically and experimentally present an optimal design for achieving near-full energy conversion while maintaining good TEM00 mode property of fundamental laser radiation in the nanosecond regime.

Comparison of high average-power femtosecond green and ultraviolet laser emissions generated by K3B6O10Br and K3B6O10Cl nonlinear crystals

We investigate the second harmonic generation (SHG) and third harmonic generation (THG) processes of femtosecond (fs) laser that occurred in type Ⅰ phase-matched K3B6O10X (X = Cl, Br; KBOC and KBOB) crystals. The high average power of 515 nm green and 343 nm ultraviolet (UV) fs lasers output were efficiently generated from these two crystals with an incident fundamental 773 fs 1030-nm laser source. Experimental results show that the highly effective nonlinear coefficient of the KBOC crystal causes higher harmonic conversion efficiency than that of KBOB crystal in the same fundamental laser parameters. The average power of 10.4 W 515 nm green and 4.6 W 343 nm UV lasers output were obtained from two pieces of 4.5 mm KBOC crystals, corresponding to 42.3 % and 19.7 % high optical conversion efficiency respectively, without temporal pulse walk-off time compensation between 1030 nm and 515 nm laser pulses. Our research will stimulate in-depth research on nonlinear frequency conversion in nonlinear optical systems and have potential applications in future applications.

Optimization of [formula omitted] femtosecond pulse laser tripling efficiency based on temporal walk-off compensation

Ultraviolet (UV) femtosecond lasers with a high repetition rate have important applications, especially in processing brittle materials. However, the group velocity walk-off limits the tripling efficiency of the 1μm femtosecond pulse. Without effective compensation, the tripling efficiency was generally less than 1%. In this study, by optimizing a birefringent BBO crystal to compensate the temporal walk-off in the 1.03μm tripling process, a maximum output power of 1.9 W with a repetition rate of 145 kHz at 344 nm was obtained, which implied a conversion efficiency of 30.5% from infrared (IR) to UV. The generated UV laser showed good power stability of 0.19% rms over 1 h and beam quality of M2 < 1.2. Using this scheme for other IR femtosecond lasers is promising for achieving high tripling efficiency.

Optimization of 1.03 Μm Femtosecond Pulse Laser Tripling Efficiency Based on Temporal Walk-Off Compensation

Optimization of 1.03 Μm Femtosecond Pulse Laser Tripling Efficiency Based on Temporal Walk-Off Compensation

Theoretical and experimental researches on the walk-off compensation of an intracavity doubling red laser using a twin-BIBO-crystal

We theoretically and experimentally researched on an intracavity frequency doubling red laser with walk-off compensation of bismuth borate (BIBO) for the first time, to the best of our knowledge. Through theoretical investigations, we described in detail the spatial walk-off characteristics of a BIBO crystal and discussed quantitatively the influence of different arrangements of a twin-BIBO-crystal on the output power of a second harmonic wave. Furthermore, the progress of walk-off compensation was revealed with the arrangement having the second BIBO 180° rotated along extraordinary axis. Experimentally, we found that the maximum average output power with walk-off compensation has been improved by 1.2 times compared to the uncompensated case, and the corresponding intensity profile restored from an oblique ellipse to an approximate circle.

Efficient generation of third harmonics in Yb-doped femtosecond fiber laser via spatial and temporal walk-off compensation

On the basis of a home-made femtosecond Yb-doped fiber laser, we designed a compact and efficient third harmonic generation scheme by a simple compensation plate of β-BaB2O4 crystal. The compensation plate is optimized through its thickness and cutting angle to reverse both spatial and temporal walk-off. By optimizing the parameters of the compensation plate and incident light intensity, a maximum output of 2.23 W with a repetition rate of 1 MHz at 345 nm is obtained, which implies a conversion efficiency of 23% from the infrared to ultraviolet.

补偿走离角时产生的相位失配及其补偿方法

补偿走离角时产生的相位失配及其补偿方法

Optimizing the performance of non-collinear optical parametric chirped pulse amplification via multi-pass structure based on two geometry configurations.

We propose a method for multi-pass non-collinear optical parametric chirped pulse amplification (MNOPCPA) based on two geometries, tangent phase-matching (TPM) and Poynting vector walk-off compensation (PVWC), which optimize the performance of optical parametric chirped pulse amplification (OPCPA). A feasible design scheme is also presented for use in implementing this approach. Employing this design, we construct and perform a numerical simulation, showing that back-conversion from the signal and idler to the pump can be inhibited, and that the conversion efficiency can be boosted dramatically, approaching the theoretical limit of ~64%, when amplification is nearly saturated at full bandwidth. In the MNOPCPA scheme, the output signal has a wider spectrum and a corresponding shorter Fourier-limited pulse duration with the pump being continuously depleted. A barycenter shift of the signal spot results from a spatial walk-off effect due to the pump, which can be offset and corrected well. To the best of our knowledge, this is the first demonstration of a multi-pass non-collinear OPCPA method employed the scheme of regenerative amplification.

High-power, high-repetition-rate performance characteristics of β-BaB₂O₄ for single-pass picosecond ultraviolet generation at 266 nm.

We report a systematic study on the performance characteristics of a high-power, high-repetition-rate, picosecond ultraviolet (UV) source at 266 nm based on β-BaB2O4 (BBO). The source, based on single-pass fourth harmonic generation (FHG) of a compact Yb-fiber laser in a two-crystal spatial walk-off compensation scheme, generates up to 2.9 W of average power at 266 nm at a pulse repetition rate of ~80 MHz with a single-pass FHG efficiency of 35% from the green to UV. Detrimental issues such as thermal effects have been studied and confirmed by performing relevant measurements. Angular and temperature acceptance bandwidths in BBO for FHG to 266 nm are experimentally determined, indicating that the effective interaction length is limited by spatial walk-off and thermal gradients under high-power operation. The origin of dynamic color center formation due to two-photon absorption in BBO is investigated by measurements of intensity-dependent transmission at 266 nm. Using a suitable theoretical model, two-photon absorption coefficients as well as the color center densities have been estimated at different temperatures. The measurements show that the two-photon absorption coefficient in BBO at 266 nm is ~3.5 times lower at 200°C compared to that at room temperature. The long-term power stability as well as beam pointing stability is analyzed at different output power levels and focusing conditions. Using cylindrical optics, we have circularized the generated elliptic UV beam to a circularity of >90%. To our knowledge, this is the first time such high average powers and temperature-dependent two-photon absorption measurements at 266 nm are reported at repetition rates as high as ~80 MHz.

Enhancement of ultraviolet-beam generation through a double walk-off compensation

We propose a novel walk-off-compensation method for ultraviolet-light-source development. A walk-off occurring in the frequency mixing of infrared and green beams is doubly compensated for using an external walk-off compensator and a nonlinear-material set with internal walk-off-compensation arrangement. We theoretically and experimentally verified that our method can improve the power and beam shape of the output ultraviolet beam.

Highly efficient 355 nm UV generation with non-collinear phase-matching by a prism-coupled device based on CsLiB6O10

We report 355 nm third-harmonic generation (THG) of UV light using CsLiB6O10 (CLBO). To compensate for the walk-off angle in THG by Type II CLBO, we designed a prism-coupled device that takes advantage of non-collinear phase-matching. This new device, equipped with a Nd:YVO4 laser source, achieved THG with 1.86 W at 47.6% conversion efficiency from the second-harmonic input. This result marks a 1.43-fold improvement over a conventional CLBO crystal, thus validating the effectiveness of the design for walk-off compensation in Type II THG. This is also the first time THG has been achieved using CLBO.

High-power 355 nm third-harmonic generation with effective walk-off compensation of LBO

Walk-off compensation using wedged cut type-II LBO was investigated theoretically and experimentally. An algorithm is proposed to find the optimized wedged cut angle to compensate the walk-off effect completely. Using a pulsed Nd:Y V O4 MOPA laser as the fundamental frequency infrared (IR) source, 36.3 W 355 nm frequency converted ultraviolet (UV) light was obtained using an optimized wedged cut type-II LBO for walk-off compensated third-harmonic generation (THG), giving a conversion efficiency of 37.1% from IR to UV. A comparative experiment using a conventional cut type-II LBO was also implemented. The results indicate that optimized wedged cutting of type-II LBO is an effective approach for walk-off compensation in efficient THG. The output performance of angle and temperature tuning for wedged cut type-II LBO was also investigated.

A picosecond widely tunable deep-ultraviolet laser for angle-resolved photoemission spectroscopy

We develop a picosecond widely tunable laser in a deep-ultraviolet region from 175 nm to 210 nm, generated by two stages of frequency doubling of a 80-MHz mode-locked picosecond Ti:sapphire laser. A β-BaB2O4 walk-off compensation configuration and a KBe2BO3F2 prism-coupled device are adopted for the generation of second harmonic and fourth harmonics, respectively. The highest power is 3.72 mW at 193 nm, and the fluctuation at 2.85 mW in 130 min is less than ±2%.

Beam steering using optical parametric amplification in Kerr medium: a space-time analogy of parametric slow-light

In a way analogous to a light pulse that can be optically delayed via slow light propagation in Kerr-type nonlinear media, we theoretically demonstrate that beam steering and spatial walk-off compensation can be achieved in noncollinear optical parametric amplification. We identify this effect as a result of the quadratic phase shift induced by parametric amplification that leads to the cancellation of the spatial walk-off and collinear propagation of all beams though they have different wavevectors. Experimental evidence is reported of a soliton array steering in a Kerr slab waveguide.

High-quality polarization entanglement state preparation and manipulation in standard telecommunication channels

We report a simple and practical approach for generating high-quality polarization entanglement in a fully guided-wave fashion. Both deterministic pair separation into two adjacent telecommunication channels and the paired photons' temporal walk-off compensation are achieved using standard fiber components. Two-photon interference experiments are performed, both for quantitatively demonstrating the relevance of our approach and for manipulating the produced state between bosonic and fermionic symmetries. The compactness, versatility and reliability of this configuration makes it a potential candidate for quantum communication applications.

Singly resonant optical parametric oscillator based on adhesive-free-bonded periodically inverted KTiOPO_4 plates: terahertz generation by mixing a pair of idler waves

We implemented a singly resonant optical parametric oscillator based on adhesive-free-bonded periodically inverted KTiOPO4 plates. It has major advantages such as walk-off compensation and oscillation at four wavelengths. The threshold of the oscillation was measured to be 8 MW/cm2, which is about a factor of 4 lower than that based in two separate KTiOPO4 crystals. By frequency-mixing the dual-wavelength output in GaP stacks, we generated the terahertz radiation at 2.54 THz. The tuning range of the terahertz output was demonstrated to be 2.19-2.77 THz.

Nano-scale sensing transducer using entangled photon walk-off compensation

We propose a new concept of a nano-sensing transducer system using a nano-waveguide. The small change in physical quantity affects to the change in device parameters such as refractive index or length which is relatively absorbed and observed by the resonant signals. In principle, the stored light pulse at the specified wavelength is generated by using a soliton propagating within the ring resonators, whereas a resonant signals can be stored within the nano-waveguide, i.e. a sensing transducer, which is formed by the sensing ring device. The induced change in the resonant signals by the surrounded environment is occurred, and can be detected by using the optical/quantum processor. Such a proposed device is namely suitable to perform the measurements in the nano-scale regime such as force, stress and temperature.

Optical parametric oscillations of 2 μm in multiple-layer bonded walk-off compensated KTP stacks

Spatial walk-off can severely increase the threshold of critical phase-matched optical parametric oscillations (OPOs) and distort the output beam quality. With 16-layer KTP stacks for walk-off compensation, noncritical phase-match-like (NCPM-like) and quasi-phase-match-like OPOs with enhanced angular acceptance have been demonstrated based on two different KTP bonding orientations. In the NCPM-like composite, output pulse energy of 49 microJ has been achieved at pump energy of 523 microJ with pulse duration of 15 ns and repetition rate of 1 KHz. The OPO threshold as low as 254 microJ(44.6 MW/cm(2)) has been achieved.

Self calibration in a fiber optic sensing system using the entangled photon states walk-off compensation

We present a concept of a self calibration of the classical and quantum parameters measurement using a fiber optic system. The measurement of the change in phase of the optimum entangled states visibility, which is performed in term of a walk-off length, i.e. birefringence. The applied two physical parameters (i.e. force/stress and temperature) on the sensing fiber can be simultaneously measured, whereas the self calibration respecting to the entangled photon walk-off length can be performed. The scheme of the entangled photons generation in fiber optic is reviewed and the walk-off on the polarization entangled states presented. The potential of self calibration and simultaneous measurement using an interferometric sensing technique and fiber grating sensor are proposed and discussed. The entangled photon walk-off compensation when the sensing fiber was in the thermal controlled environment presented and discussed.