Sum-frequency mixing

Sum-frequency mixing of two solid-state YAG lasers in a nonlinear crystal (see Ch. 20) to generate 589 nm in CW, CW mode-locked and macromicro pulse formats. The Nd YAG lasers can be pumped by flashlamps, but higher efficiency is obtained using diode lasers. 

Sum-frequency mixing of two diode pumped fiber lasers (938 and 1583 nm) in a nonlinear crystal. CW format has been demonstrated at low power levels higher powers and pulsed formats are under development. 

Figure 16. Sum-frequency mixing two Nd YAG lasers at 1064 and 1319 nm in a nonlinear crystal produces 589 nm light.

Gemini North Observatory/CTI Mode-locked SFG Laser. CTT is developing the first commercial solid-state Na LGS system. It will be installed on the center section of the 8-m Gemini North telescope, with the output beam relayed to a projector behind the secondary mirror. The projected beam is required to be 10-20 W power, with M2 < 1.5. The architecture is based on sum-frequency mixing two mode-locked solid-state Nd YAG lasers. The mode-locked format provides significantly higher peak intensity than CW, enabling more efficient SFG conversion. The laser is also free of the thermal and intensity transients that are inherent in the macro pulse format. The chosen... 

The double-beam transient absorption spectrometer utilized in this work is described in detail elsewhere [3]. Briefly, the output from a 1 kHz Ti Sapphire laser is frequency quadrupled to generate the 200 nm photolysis pulses. The probe pulses are generated by frequency doubling the output of an optical parametric amplifier (OPA) pumped at 400 nm or by sum-frequency mixing of the OPA output with 400 nm and 800 nm pulses. The sample consisted of a 0.1 mm jet of aqueous KNO3 solution. The acidity of the solutions was adjusted by addition of HN03(aq). 

Experiments were performed using a commercial kilohertz femtosecond Ti Sapphire laser system (Spectra Physics) delivering laser pulses at 790 nm with a duration of 110 fs and an energy of 750 pj. The pump beam at 263 nm (third harmonic) was produced by frequency doubling and sum-frequency mixing in two BBO crystals. Then, the pump beam was focused on a 300 pm thick ethylene glycol jet in order to produce electrons by photoionisation of the... 

Figure 6. Instrumental schematic for vacuum UV photofragmentation-laser induced fluorescence measurement of ammonia SHGC, second harmonic generation crystal SFMC, sum frequency mixing crystal BS, beam splitter BD, beam dump TP, turning prism CL, cylindrical lens R, reflector TD, trigger diode OSC, oscillator cell AMP, amplifier cell BE, beam expander G, grating OC, output coupler M, mirror BC, beam combiner L, lens A, aperture PD, photodiode SC, sample cell RC, reference cell FP, filter pack SAM.PMT, sample cell photomultiplier REF.PMT, reference cell photomultiplier PP, additional photomultiplier port EX, exhaust and CGI, calibration gas inlet to flow line. (Reproduced with permission from reference 15. Copyright 1990 Optical Society of America.)...

In general, x<3> is several orders of magnitude smaller than x(2) [78]. However, this contribution can be comparable to the second-order response when the dc field is large (i.e. 104 — 105 V/cm) as is the case for a metal electrode in solution held at a bias on either side of the PZC. The SH fields can be viewed as arising from a sum frequency mixing process where two incident ac fields at frequency co are mixed with a dc field at frequency co = 0 to produce a reflected and transmitted wave at frequency 2co. 

We have demonstrated this effect in two experiments [13,14]. One is in single frequency ultraviolet generation by sum frequency mixing and the other is in Doppler-free two-photon spectroscopy, with the FM laser. 

The results to-date have really only sampled a small fraction of the possible atomic and molecular systems that could be used for nonlinear materials in VUV harmonic generation. Thus, there is no longer any doubt that all of the spectral region between 1000 A and 2000 A can be spanned by means of sum-frequency mixing from the visible and near-ultraviolet. We will now outline the theory on which these processes are based. 

R.R. Freeman, G.C. Bjorklund, N.P. Economou, P.F. Liao, J.E. Bjorkholm, Generation of cw VUV coherent radiation by four-wave sum frequency mixing in Sr vapor, Appl. Phys. Lett. 33 (1978) 739. 

In two-photon ionization the first photon excites polymers to an electronic state and a second photon ionizes the excited molecules. This approach has the following advantages over single-photon ionization. One can employ commercial lasers, avoiding the complication of sum frequency mixing or other schemes for VUV generation. Typical lasers for this purpose include the quadrupled Nd YAG laser and excimer lasers. Two-photon processes in the absence of saturation of both steps depend quadratically on laser power. 

Kaminskii AA, Rhee H, Eichler HJ, Ueda K, Takaichi K, Shirakawa A et al (2008) New nonlinear-laser effects in crystalline fine-grained ceramics based on cubic SC2O3 and LU2O3 oxides second and third harmonic generation, and cascaded self-sum-frequency mixing in UV spectral region. Laser Phys Lett 5 109-113... 

The early work of Harris and coworkers [27] on nonlinear mixing in Xe and Ar was followed by work on Kr and Xe. Extensive wavelength tunability with rare gases was reported by Hilbig and Wallenstein [28]. The used sum-frequency mixing (o)VUV = 2o)uv + d) Xe to generate... 

I.Z. Kozma, P. Baum, S. Lochbrenner, E. Riedle, Widely tunable sub-30-fs ultraviolet pulses by chirped sum-frequency mixing. Opt. Express 11, 3110 (2(X)3)... 

Marangos JP, Shen N, Al HME (1990) Broadly tunable vacuum-ultraviolet radiation source employing resonant enhanced sum-frequency mixing in krypton. J Opt Soc Am B 7 1254-1259... 

Third harmonic, four wave sum-frequency mixing, four-wave difference-frequency mixing Infrared (3.3 fim) to XUV (57 nm) CO2, CO, Nd, ruby, dye, excimer Rare gases, molecular gases, metal vapors, cryogenic liquids... 

The intensity of the generated radiation grows as the product of the incident pump intensities at low conversion efficiency. In the three-wave sum-frequency mixing interaction, one photon from each of the pump waves is annihilated for each photon created in the generated wave. Complete conversion of the total radiation in both pump waves at perfect phase matching is possible in principle if they start with an equal number of photons. Otherwise the conversion will oscillate with pump intensity or crystal length, even at exact phase matching. 

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