Tunable terahertz wave generation in the 3- to 7-THz region from GaP

Abstract

Following the generation of tunable terahertz waves from GaP in the 0.5- to 3-THz region, we extended the frequency region up to 7 THz, using an optical parametric oscillator and a YAG laser (1.064 μm). The tuning angle θin increased superlinearly in the 3- to 7-THz region, so that the total reflection took place at 5 THz, which was avoided by rotating the crystal relative to the incident optic axis. As a result, terahertz output peak powers of 100 mW at up to 5.6 THz and 3 mW at 7 THz were obtained, at pump and signal energies of 3 mJ, respectively.

Analysis of the specific vibration modes of goethite (α-FeOOH) by terahertz spectroscopy and calculations of the vibration frequencies of a single molecule using density functional theory

“…When Fe(OH) 3 is hydrolyzed, α-FeOOH is formed. In contrast, if the oxidation rate is slow, green rust, which is a mixture of Fe(OH) 2 and Fe(OH) 3 is produced. When the green rust is completely oxidized, it changes to α-FeOOH [13][14] .…”

“…It has since become possible to make measurements over a wide range of tunable frequencies using difference frequency generation (DFG) crystals, which have high nonlinear optical effects. Thus, we have devoted much attention to studying this phenomenon [2][3][4] . As THz spectroscopy has developed, the infrared activities of many organic and biological substances have been reported [5][6][7][8][9][10] ; however, the infrared activity of…”

“…When Fe 3+ ions are generated in steel sheet, they aggregate in neutral or basic solutions to form colloids of Fe(OH) x 3-x . If the oxidation rate is fast, the Fe 3+ ion deprotonates into Fe(OH) 3 . When Fe(OH) 3 is hydrolyzed, α-FeOOH is formed.…”

Fabrication and Characterization of GaP Photonic Crystals for Terahertz Wave Application

“…The most THz-wave sources are based on photoconductive antenna, quantum cascade lasers, or non-linear optical effects such as difference frequency generation (DFG), optical parametric oscillation, and optical rectification. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The DFG can produce tunable, narrow linewidth, and high power THz-waves with ns-pulsed as well as CW operation. 18,19) The THz-waves can be generated at room temperature.…”

“…[7][8][9][10][12][13][14]20) In addition, our previous works have generated THz-waves with bulk GaP crystals under a small-angle non-collinear phase matched DFG condition. [7][8][9] By using the THz wave source, a frequencytunable THz spectrometer has constructed, and the THz spectra of important biomolecules (e.g. sugars, nucleosides, nucleotides, amino acids, etc.)…”