Frequency Doubling Of Laser Diode Research Articles

Efficient continuous wave deep ultraviolet Pr3+:LiYF4 laser at 261.3 nm

We report continuous wave deep ultraviolet laser operation at 261.3 nm by intracavity frequency doubling of laser diode pumped Pr3+ doped LiYF4 lasers. Using two InGaN laser diodes with a maximum output power of about 1 W each, a 2.9 mm long Pr3+:LiYF4 crystal and a 5 mm long beta-barium-borate crystal, coherent radiation with an output power of 481 mW at 261.3 nm was achieved at an optical-to-optical efficiency of 26.1% with respect to the total pump power. Both, linear and nonlinear losses have been calculated to be approximately 0.6% by using a model for intracavity frequency doubling with focussed Gaussian beams.

Compact continuous-wave blue lasers by direct frequency doubling of laser diodes with periodically poled lithium niobate waveguide crystals

A compact continuous-wave blue laser has been demonstrated by direct frequency doubling of a laser diode with a periodically poled lithium niobate (PPLN) waveguide crystal. The optimum PPLN temperature is near 28 degrees C, and the dependence of waveguide crystals on crystal temperature is less sensitive than that of bulk crystals. A total of 14.8 mW of 488-nm laser power has been achieved.

Study on the micro-crystallization of cadmium mercury thiocyanate (CMTC) crystal for laser diode frequency doubling

The habit of cadmium mercury thiocyanate (CMTC) crystal for laser diode frequency doubling when crystallized from KCl–H 2O solutions at 28°C under different conditions was investigated by means of a micro-crystallization method. The results show that CMTC crystals exhibit a regular crystalline morphology, homogenous growth rate in different directions and are transparent when the concentration of KCl ranges from 3% to 10% and pH from 3.0 to 4.0. Decrease in pH value leads to an increase in the crystallization rate along the c-axis direction, and a decrease along the a-axis direction. Impurities greatly affect the crystalline quality and morphology of the crystal. With aging and increasing temperature the solution becomes unstable. In this paper, suitable conditions and key factors for CMTC crystal growth are discussed.

Growth of cadmium mercury thiocyanate single crystal for laser diode frequency doubling

Cadmium mercury thiocyanate (CdHg(SCN) 4, CMTC) crystal is one of the most efficient nonlinear optical crystals among complex crystals. Two different solvent mixtures of water–NaCl and water–KCl suitable for growing CMTC crystal are reported for the first time. A typical single crystal of CMTC with size 18×18×25 mm 3 was grown from a water–NaCl mixture solvent by using temperature-lowering method.

Structure and properties of a complex crystal for laser diode frequency doubling: Cadmium mercury thiocyanate

The crystal structure of cadmium mercury thiocyanate [CdHg(SCN)4] is determined by means of a four circle diffractometer. The structural features and properties of the crystal are described. Blue-violet light output by frequency doubling of a 809 nm GaAlAs laser diode using a cadmium mercury thiocyanate crystal device that is 3 mm thick at the phase matching angle: θ=47.7°, φ=0°, is realized at room temperature with input power lower than 200 mW. A 404.5 nm light output power of 1.8 mW is also measured for a 576 mW input power of the GaAlAs laser diode.

Generation of 340-nm light by frequency doubling of a laser diode in bulk periodically poled LiTaO_3

Frequency doubling of a 680-nm laser diode in periodically poled LiTaO(3) is presented. By selective proton exchange followed by high-voltage pulse application, a second-order periodic domain inversion having uniform periodicity and optimum duty cycle was fabricated over a 10-mm interaction length in a 200-microm-thick LiTaO(3) substrate. A 340-nm wavelength of harmonic ultraviolet light was generated in a single pass through the domain-inverted structure.

High second-harmonic conversion efficiency of quasi-phase-matched LiTaO3 waveguides pumped by single-mode pulsed AlGaAs laser diodes

We show that the averaged second-harmonic conversion efficiency of quasi-phase-matched LiTaO3 waveguides can be increased by a factor larger than 15 with the use of single-mode pulsed AlGaAs laser diodes as the optical sources. The proton exchange followed by thermal annealing is used both to periodically change the sign in d33 nonlinear coefficient and to fabricate the waveguides. Laser pulses are produced by strong rf modulation of the diode current while single-mode operation is achieved with a grating-tuned external cavity. The averaged conversion efficiency is found to linearly increase with peak power of pulses even in the case of pulses whose spectral width is larger than the spectral acceptance of LiTaO3 waveguides. Experimental results are in agreement with calculated ones. The conversion efficiency of 450 %/W presently reached at optimum (i.e., 1% for 2.2 mW pump and 1 cm interaction length) is among the highest performances reported to date for frequency doubling of laser diodes.

Preparation and characterization of organic thin film for semiconductor laser frequency doubling

Organic non-linear optical (NLO) materials hold the promise of realizing blue, second harmonic generation (SHG) semiconductor lasers, which have versatile applications due to their large nonlinearities. Among the organic NLO materials known today, conjugated benzene derivative compounds, which have been studied most extensively, have the largest non-linear effects. At the same time, they often have large birefringences and a red-shifted cut-off (>500 nm). These shortcomings have significantly influenced their applications in frequency doubling. 3-Methoxy-4-hydroxy-benzaldehyde (MHBA), grown in our laboratory, is an excellent organic NLO material. Its cut-off is at 375 nm, but it still has large NLO coefficients and relatively small birefringences [1,2]. Even so, MHBA still cannot realize non-critical phase matching (NCPM) in the spectral region of the GaA1As series laser, which is an important factor influencing the blue SHG of lower power laser diodes. Recently, SHG in an organic single-crystalline optical waveguide demonstrated new potentials in laser diode frequency doubling [3, 4]. In this letter, we describe the growth and characterization of MHBA single-crystalline film. MHBA single-cryStalline film was prepared by the Bridgman method. Before film growth, two polished fused quartz substrates (20 x 30mm) were thoroughly cleaned. The paired substrates were dipped into the MHBA melt in a glass tube controlled at a temperature of 95 °C (compared with its melting point of 83 °C). Capillary action ensured that the melt could penetrate into the gap between the two substrates. When the temperature cooled to room temperature the film in the gap was composed of randomly oriented small crystals. After melt penetration, the film inside the substrates was recrystallized to make a large-area single-crystalline film, using the apparatus shown in Fig. 1. The MHBA polycrystalline film inside the paired substrates was suspended and lowered through the growth region in a stove at a motor-controlled rate of 0.3 mmh -1 for recrystallization. In our experiments, the largest area of the grown film was up to 10 x 10 ram. The quality of the prepared film depended on several factors: the cleaning and polishing of the substrates, the temperature distribution in the stove, the stability of the whole growth apparatus, the down speed of the substrates and the purity of raw materials.

Frequency-doubled monolithic master oscillator power amplifier laser diode

Single-pass frequency doubling of laser diodes extends the wavelength range of infrared laser diodes to blue-green wavelengths. We describe the first experiments of frequency doubling of a coherent, high-power, monolithic master oscillator power amplifier (M-MOPA) laser diode. The output from a l-W M-MOPA is frequency doubled in a single pass through an 8.2-mm-long KNbO/sub 3/ crystal. We obtained 3.7-mW diffraction-limited output power at a wavelength of 491 nm and modulation at 20 MHz was demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Special Issue on Nonlinear-Optic Waveguide Materials and Devices. LiTaO3 Quasi-Phase-Matched Second-Harmonic-Generation Device.

Quasi-phase-matched second-harmonic-generation (QPM-SHG) is an attractive method for obtaining blue light, as phase-matching of an arbitrary wavelength may be achieved by appropriate periodic modulation of the nonlinear polarization. This paper describes recently reported QPM-SHG in waveguides, especially QPM-SHG in LiTaO3, which has large non-linearlity and high resistance to optical damage. Recent experiments in frequency doubling of laser diodes using the QPM-SHG device are also described.

Generation of ultraviolet picosecond pulses by frequency-doubling of laser diode in proton-exchanged MgO:LiNbO/sub 3/ waveguide

Ultraviolet picosecond pulses were generated by frequency doubling a AlGaAs-GaAs laser diode in a proton-exchanged waveguide fabricated in MgO:LiNbO/sub 3/. The Cerenkov radiation scheme was used to phase-match the infrared pulse from a gain-switched laser diode, which operates in multilongitudinal modes. Pulses with a peak power of 1.35 mW and 19.3-ps width were obtained at 390 nm. This is a unique method for generating short ultraviolet pulses with laser diodes in a simple configuration. >

A Nonlinear Optical Organic Crystal for Waveguiding SHG Devices: (-)2-(α-Methylbenzylamino)-5-Nitropyridine (MBANP)

A nonlinear optical organic material, (-)2-(α-methylbenzylamino)-5-nitropyridine (MBANP), has been comprehensively investigated with the objective of application to frequency doubling of laser diodes. Its molecular hyperpolarizability is as large as that of p-nitroaniline. MBANP crystallizes with a highly asymmetric molecular arrangement. The largest nonlinear optical coefficient, d22, is measured to be 60 pm/V. The corresponding figure of merit for frequency doubling at 1.064 µm is 3.5 times larger than that for d33 of LiNbO3. Čerenkov-radiation-type, phase-matched second-harmonic generation has been demonstrated utilizing the d22 coefficient by making use of an appropriate waveguiding structure.