Frequency doubler

Optical second-harmonic generation (SHG) has recently emerged as a powerful surface probe [95, 96]. Second harmonic generation has long been used to produce frequency doublers from noncentrosymmetric crystals. As a surface probe, SHG can be caused by the break in symmetry at the interface between two centrosymmetric media. A high-powered pulsed laser is focused at an angle of incidence from 30 to 70° onto the sample at a power density of 10 to 10 W/cm. The harmonic is observed in reflection or transmission at twice the incident frequency with a photomultiplier tube. 

Commercial frequency doublers have rehed on inorganic materials. The commercial future of doublers depends on not only the improvement in second-order materials but also the development of diode lasers capable of operating in the visible frequency domain. 

The nonlinear optical and dielectric properties of polymers find increasing use in devices, such as cladding and coatings for optical fibres, piezoelectric and optical fibre sensors, frequency doublers, and thin films for integrated optics applications. It is therefore important to understand the dielectric, optical and mechanical response of polymeric materials to optimize their usage. The parameters that are important to evaluate these properties of polymers are their dipole moment polarizability a, hyperpolarizabilities 0... 

Frequency-doubled Ar ion lasers, 19 115 Frequency doublers, commercial,... 

Figure 28.11 Apparatus for photoemission measurements. L, Q-switched ruby laser d, frequency doubler F, CuS04 solution filter SR, screened room D, diaphragm PD, photodiode SO, storage oscilloscope C, cell P, polarizing circuit A, wideband amplifier O, oscilloscope. The mercury pool working electrode is renewed continuously from the reservoir at the upper right. [From Ref. 61.]...

From these results, As the particular tensor component of DAD molecular crystal is expected to be very high, more than 2-methyl-4-nitroaniline(MNA)(20), it would become one of the most suitable materials of highly efficient optical device for frequency doubler by using phase matching with optical wave guide. Electro-optical properties as well may be interesting. 

Figure 2. A typical experimental arrangement for measuring CARS spectra. FD denotes frequency doubler, KG3 is a 1.06-pm absorbing filter, L is for lens, g is a grating, DC is a dye cell, D is a dichroic beam splitter, m is a mirror, and P is a prism (9).

FIGURE 10. Schematic drawing of a ZEKE experimental setup QD, quadrant diode PD, photodiode CP, channel plate detector INT, integrator SMS, stepping motor drive FL, dye laser ADC, analog to digital converter PI/O, output/ input port SHG, frequency doubler X, point of interaction. Reproduced by permission of the American Institute of Physics from Reference 27... 

Figure 1. Schematic of the apparatus. AC-absorption cell, BPF-bandpass filter, CdL-cadmium lamp, CM-capacitaiice manometer, D-frequency doubler, DG-three channel delay generator, DC-dye laser, EM-emergy monitor, Gl-gas inlet, HS-harmonic separator, HV-high voltage, PA-picoammeter, PD-photodiode, PM-photomultiplier, PL-photolysis laser, RC-reaction cell, SA-signal averager, T-chrottle, YL-Nd YAG laser, 7-54F-Corning 7-54 glass filter.

In contrast, the nonlinearities in bulk materials are due to the response of electrons not associated with individual sites, as it occurs in metals or semiconductors. In these materials, the nonlinear response is caused by effects of band structure or other mechanisms that are determined by the electronic response of the bulk medium. The first nonlinear materials that were applied successfully in the fabrication of passive and active photonic devices were in fact ferroelectric inorganic crystals, such as the potassium dihydrogen phosphate (KDP) crystal or the lithium niobate (LiNbO,) [20-22]. In the present, potassium dihydrogen phosphate crystal is broadly used as a laser frequency doubler, while the lithium niobate is the main material for optical electrooptic modulators that operate in the near-infrared spectral range. Another ferroelectric inorganic crystal, barium titanate (BaTiOj), is currently used in phase-conjugation applications [23]. 

In recent years there has been a growing interest in the search for materials with large macroscopic second-order nonlinearities [20-22] because of their practical utility as frequency doublers, frequency converters and electro-optic modulators [23] by means of second-harmonic generation, parametric frequency conversion (or mixing) and the electro-optic (EO) effect. They are described by X (2w w, u)), 0, w), respectively. In order to optimize... 

Another metal phosphate important for electronic applications is KTP (KTiOP04), used as a frequency doubler for solid state lasers. Again sub-... 

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