A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

The absorption and emission properties of transition metal (TM)-doped zinc chalcogenides have been investigated to understand their potential application as room-temperature, mid-infrared tunable laser media. Crystals of ZnS, ZnSe, and ZnTe, individually doped with Cr/sup 2+/, Co/sup 2+/, Ni/sup 2+/, or Fe/sup 2+/ have been evaluated. The absorption and emission properties are presented and discussed in terms of the energy levels from which they arise. The absorption spectra of the crystals studied exhibit strong bands between 1.4 and 2.0 /spl mu/m which overlap with the output of strained-layer InGaAs diodes. The room-temperature emission spectra reveal wide-band emissions from 2-3 /spl mu/m for Cr and from 2.8-4.0 /spl mu/m for Co, Cr luminesces strongly at room temperature; Co exhibits significant losses from nonradiative decay at temperatures above 200 K, and Ni and Fe only luminesce at low temperatures, Cr/sup 2+/ is estimated to have the highest quantum yield at room temperature among the media investigated with values of /spl sim/75-100%. Laser demonstrations of Cr:ZnS and Cr:ZnSe have been performed in a laser-pumped laser cavity with a Co:MgF/sub 2/ pump laser. The output of both lasers were determined to peak at wavelengths near 2.35 /spl mu/m, and both lasers demonstrated a maximum slope efficiency of approximately 20%. Based on these initial results, the Cr/sup 2+/ ion is predicted to be a highly favorable laser ion for the mid-IR when doped into the zinc chalcogenides; Co/sup 2+/ may also serve usefully, but laser demonstrations yet remain to be performed.

Transition metal-doped zinc chalcogenides: Spectroscopy and laser demonstration of a new class of gain media

Frequency down-conversion of solid-state laser sources to the mid-infrared spectral range using non-oxide nonlinear crystals

2D Layered Materials: Synthesis, Nonlinear Optical Properties, and Device Applications

Mid-infrared (IR) nonlinear optical (NLO) materials with high performance are vital to expanding the laser wavelengths into the mid-IR region and have important technological applications in many civil and military fields. For the last two decades metal chalcogenides have attracted great attention since many of them possess a large NLO effect, wide transparent range, moderate birefringence, and high resistance to laser damage. However, the discovery of superior mid-IR NLO metal chalcogenides is still a big challenge mainly due to the difficulty of achieving a good balance between the NLO effect and laser damage threshold (LDT). In this review, metal chalcogenides are catalogued according to the different types of microscopic building blocks. These groups include triangle planar units, tetrahedral metal-centered units, polyhedra with second-order John-Teller cations, and polyhedra with stereochemically active lone electron pairs cations, rare-earth cations, and/or halogen anions. The determinations of thes...

Mid-Infrared Nonlinear Optical Materials Based on Metal Chalcogenides: Structure–Property Relationship

An efficient 2 μm in-band pumped Ho:YAG laser was demonstrated The resonator involves two Ho:YAG crystals, each of which was dual-end-pumped by two orthogonally polarized diode-pumped Tm:YLF lasers The maximum continuous wave output power of 103 W was achieved, corresponding to a slope efficiency of 678% with respect to the incident pump power and an optical-to-optical conversion efficiency of 635% Under Q-switched mode, we obtained 101 W laser output at 30 kHz, corresponding to a slope efficiency of 662% The beam quality or M2 factor was found to be less than 2

103 W in-band dual-end-pumped Ho:YAG laser.

High power and high beam quality continuous wave Tm:YLF laser by the dual-end-pumped is presented in this letter. The highest output power reaches 21.3 W when the totally input pump power is 54.6 W. The optical conversion efficiency is 39.0% and the slope efficiency is 47.3%. With an F-P etalon in the cavity, the output center wavelength is tuned to 1908 nm with about 0.5 nm FWHM. With the optimal cavity, the beam quality factor M2 can be ~ 1.1. As we know, our work is the first time to investigate the Tm:YLF laser output spectrum with an F-P etalon in the cavity, and acquire near-diffraction limited laser output.

Diode-pumped high efficient Tm:YLF laser output at 1908 nm with near-diffraction limited beam quality

We reported a high-power ZnGeP₂ (ZGP) optical parametric oscillator (OPO) pumped by a Q-switched Ho:YAG laser. The maximum output power of the ZGP OPO was 41.2 W at 107.0 W incident Ho pump power, corresponding to a slope efficiency of 44.6%. The ZGP OPO produced 16-ns mid-IR pulse laser in the 3.74-3.98 μm and 4.38-4.76 μm spectral regions simultaneously. The beam quality was measured to be M²<4.37. The continuous wave maximum average output power of the Ho:YAG laser was 128 W, corresponding to a slope efficiency of 65.8%.

A 41-W ZnGeP_2 optical parametric oscillator pumped by a Q-switched Ho:YAG laser

The active/passive Q-switching operation of a 2 μm a-cut Tm,Ho:YAP laser was experimentally demonstrated with an acousto-optical Q–switch/MoS2 saturable absorber mirror. The active Q-switch laser was operated for the first time, to the best of our knowledge, with an average output power of 12.3 W and a maximum pulse energy of 10.3 mJ. The passive Q-switch laser was also the first acquired with an average output power of 3.3 W and per pulse energy of 23.31 μJ, and the beam quality factors of Mx2=1.06 and My2=1.06 were measured at the average output power of 2 W.

Active/passive Q-switching operation of 2 μm Tm,Ho:YAP laser with an acousto-optical Q-switch/MoS 2 saturable absorber mirror

We report the room temperature continuous wave and acousto-optically Q-switched Ho:YAG laser double-pass pumped by a diode-pumped Tm:YLF laser. Continuous wave output power of 10.5 W at 2090 nm is obtained under the incident pump power of 18.1 W, corresponding to a conversion efficiency of 58.0% and a slope efficiency of 65.7%. For the Q-switched regime the maximum pulse energy of 1.0 mJ and the minimum pulse width of 25 ns at the repetition rate of 10 kHz are achieved, resulting in a peak power of 40.0 kW.

Xiaoming Duan

Papers

103 W in-band dual-end-pumped Ho:YAG laser.

Diode-pumped high efficient Tm:YLF laser output at 1908 nm with near-diffraction limited beam quality

A 41-W ZnGeP_2 optical parametric oscillator pumped by a Q-switched Ho:YAG laser

Active/passive Q-switching operation of 2 μm Tm,Ho:YAP laser with an acousto-optical Q-switch/MoS 2 saturable absorber mirror

Room temperature efficient continuous wave and Q-switched Ho:YAG laser double-pass pumped by a diode-pumped Tm:YLF laser