The response speed and fatigue characteristics of a pulsed 778 nm -> 420 nm conversion in rubidium vapor

A strong 778 nm -> 420 nm conversion was realized in Rb vapor. With the help of the multi-spike structure of the 778 nm pumping laser, the response speed of the 778 nm -> 420 nm conversion was successfully measured. Experimental results showed that the conversion was a high-speed process, with a response bandwidth of 1 GHz. In addition, fatigue phenomenon of the 778 nm -> 420 nm conversion under strong pumping was observed, and the recovery time of such fatigue was measured with a dual pump method. (C) 2016 Elsevier B.V. All rights reserved

Potassium upconversion violet light generation under two-color two-photon excitation to 4D, 6S level

Two-color nanosecond dye lasers were used to excite potassium vapor cell, and 404-nm violet beam output was observed. This violet beam owns good collimation and transient properties, and its wavelength matches with the transition from potassium 52P3/2,1/2 doublet to the ground state. An analysis process shows that the violet light mechanism is attributed to two-photon-induced 42S1/2 → 42P3/2 → 42D3/2,5/2/62S1/2 transition, 42D3/2,5/2/62S1/2 → 52P3/2,1/2 SHRS (stimulated hyper-Raman scattering), and FWM (four-wave-mixing) processes; this is a third-order nonlinear optics process. Violet light doublet-line intensity ratio was found to change while fine scanning of excitation wavelength; this shifting was thought related to the FWM resonant degree. Potassium violet light is expected to become new tunable light source

Method to improve the resolution o a non-parallel Fabry-Perot etalon

A new method to improve the resolution of a slightly non-parallel solid etalon is proposed. The method is aimed to reduce the spectrum broadening caused by non-parallel surfaces; it contains a theoretical formula for adjusting image distances, and an algorithm for processing the corresponding fringe patterns. Theoretical consideration, computer simulation, experimental results, and application demonstration are given. The fringe patterns captured by a CCD showed good agreement with the computer simulation, and the resolution of a lambda/10-wavefront-error etalon was improved from 3.1 GHz to 0.51 GHz. In comparison with other methods, this new method is convenient and economical. (C) 2018 Optical Society of Americ

Influence of pumping power density on output intensities and stabilities of competitive multi-line frequency up-conversions in cesium vapor

Multi-line frequency up-conversions are realized in Cs vapor using 718.8 nm pumping laser resonating with the two-photon transition 6(2)S(1/2) -> 8(2)D(5/2) of Cs atom. The pumping beam is converted into a beam including wavelengths of 361.2, 387.7, 455.7 and 621.5 nm. Experiments with collimated and focused pumping configurations are carried out and compared. Spectrum peak at 361.2 nm is strongest under collimated pumping condition, while 387.7 nm is strongest under focused pumping beam. The output beam under focused pumping is more stable than that under collimated pumping. Results in this work may be useful in laser frequency standard, beacon light, laser measuring and optics communications, etc. (C) 2017 Elsevier Ltd. All rights reserved

A robust, alignment-free broadband CARS system based on stimulated processes in heavy water

We have established a new method for realizing a typical "2-color" collinear CARS (coherent anti-Stokes Raman scattering) system. The system mainly consists of a laser source, a - D2O cell, and a spectrometer. The pump/probe beam and the Stokes beam are provided by SBS (stimulated Brillouin scattering) and BSRS (backward stimulated Raman scattering) of - D2O, respectively. The CARS system is statistically stable, and it is also a broadband and alignment-free system. Measurement of - N-2 signal in air with this system is demonstrated. Detection of - N-2 in 0.006 bar air is realized with this system. Time-resolved pulse shapes of SBS and BSRS are measured to confirm their generation. Transference of energy from the SBS pulse to the BSRS pulse is realized with a Rhodamine 101 dye cuvette and discussed. This results in a better energy distribution between the pump/probe and Stokes pulses for CARS

Powder sum-frequency generation as a versatile method for infrared optical alignment

The sum-frequency generation (SFG) in potassium dihydrogen phosphate (KDP) powder with mu m-grade particle size is successfully demonstrated under various experimental conditions. Two focused beams of 870 nm and 1369 nm are used for SFG excitation. SFG is observed under different excitation energies. The SFG intensity shows isotropy with different observation azimuths. The intersection angle between two excitation beams is not limited by conventional phase-matching conditions, and it owns the flexibility of a very large allowed range, e.g., it can be 0 degrees similar to 100 degrees in this work. The polarization combination of excitation beams is not limited either. Thanks to the non-toxicity, low price, and low SFG threshold properties of KDP material and the optical flexibility, this powder SFG technology is a versatile method and is expected to be applied to various situations of optical alignment, e.g., surface SFG, four-wave mixing, coherent anti-Stokes Raman spectroscopy, multi-color laser excitation, etc. The effect of potential powder SFG-assisted optical alignments is also discussed. Extension of this method to multi-beams, tight focusing beams, and plasmonic polariton devices is proposed. (c) 2018 Optical Society of Americ

Stable Two-Photon Pumped Amplified Spontaneous Emission from Millimeter-Sized CsPbBr3 Single Crystals

Metal-halide perovskites are promising optical gain materials because of their excellent photophysical properties. Recently, large perovskite single crystals with phase purity, less defects, and over millimeter dimensions have been successfully synthesized. However, the optical gain effect from these large-size single crystals has not yet been realized. Herein, we for the first time report efficient two-photon pumped amplified spontaneous emission (ASE) from millimeter-sized CsPbBr3 single crystals (SCs) with a low threshold of 0.65 mJ cm(-2) and an optical gain of 38 cm(-1). Furthermore, the CsPbBr3 SCs also exhibit ultrastable ASE under continuous laser irradiation for more than 40 h (corresponds to 1.5 x 10(8) laser shots) at ambient condition. This work suggests the potential application of large-size perovskite single crystals in practical nonlinear optical devices