Based on the rate equation set for broadband cavities, the dependence of pulse duration on cavity and pumping parameters is analyzed. The cavity uses a Ce-doped crystal as a gain medium. Computation results show the variation of the pulse width with the change of cavity length, mirror reflectivity, pumping energy and pumping pulse duration. A significant influence of multiple-pulse operation in limiting pulse duration is realized and a pulse-width of the order 200 ps is found to be the limit for the direct generation of ultraviolet single picosecond pulses from a Ce:LLF short cavity.

The design of a lens duct to facilitate the launching of terahertz (THz) radiation into Teflon photonic crystal fiber waveguide is presented. The InAs THz emitter, lens duct, and waveguide, collectively called THz pigtail are found to be potential mean of effectively channeling and directing THz radiation.

We present terahertz (THz) emission of optically pumped 5-nm GaAs/AlGaAs multiple quantum wells (MQWs) even at excitation energies below the bandgap. The excitation energy corresponding to the peak THz emission is red-shifted with respect to the photoluminescence (PL) and photoluminescence excitation peak. This is attributed to a transient bandgap renormalization that occurs on the same time scale as the generation of the THz transients. Moreover, an emission shoulder at ∼40meV below the THz emission peak was observed. Deep level transient spectroscopy results do not indicate that this is due to electron traps. However, an indistinct LO phonon-related, below-bandgap PL feature was seen at low temperature that coincides well with the observed THz radiation feature. It is proposed that the THz action spectrum may be sensitive to phonon-mediated processes in contrast to more conventional optical spectroscopy techniques, albeit at room temperature.

Terahertz (THz) radiation from p-type (100) InAs was investigated using time domain spectroscopy. Azimuthal angle dependence measurements and the ambipolar mobility theory suggest the dominant THz radiation mechanism to be that of the surge current.

The magnetic field orientation dependence of the terahertz radiation intensity from GaAs/AlGaAs modulation-doped structures with varying spacer thickness was investigated. Results are analyzed in the context of junction electric field, carrier mobility, and interface roughness.

A polymer-based, Cytop planar photonic crystal waveguide (PPCW) was designed for guiding terahertz radiation. Results indicate that the propagation and coupling losses in the 0.2–1.1THz range are relatively small for a sheetlike thickness design. Spectral analysis of the transmission data reveals frequency selectivity of the PPCW. Calculations of the spatial distribution of the terahertz electric field through the waveguide show evidence of single-mode propagation at a 0.45THz central frequency. The highly transparent nature of Cytop from deep ultraviolet to the far infrared region indicates its potential use as an integral component in hybrid optics.

Using femtosecond laser with short pulse duration enhances the high-frequency component of THz - radiation spectrum from n-type InAs immersed in magnetic field. Such high-frequency component is found to originate from the hybrid plasmon - longitudinal optical phonon modes.

Nonlinear absorption properties of Ce:LiCAF crystals at 266-nm wavelength are studied using open-aperture Z-scan method and a Q-switch Nd:YAG laser. Saturable absorption of solid-state materials in ultraviolet region is demonstrated for the first time.

Solid-state phase transition onset in an endocrine-disrupting estrogen-like chemical (1,4-naphthol) is detected using terahertz transmission spectroscopy. Differential scanning microscopy and temperature-dependent X-ray diffraction analysis confirmed the occurrence of such phenomenon.

THz-radiation from femtosecond-laser-irradiated InAs (100) surface is investigated. It is found that THz-radiation spectrum exhibits two inter-related phenomena in a strong magnetic field under the Voigt configuration.

Generation of terahertz pulses from photoconductive switch on zinc oxide (ZnO) single crystal is demonstrated. High transparent nature of ZnO in visible, near-infrared, mid-infrared and terahertz region will unravel the prospect of integrated active optics.

The construction of highly flexible and strongly polarization-preserving Teflon photonic crystal fiber (PCF) waveguide is discussed. This PCF has a low-loss coefficient thereby making it feasible to construct long and efficient waveguide for terahertz radiation.

Terahertz pulses generated from photoconductive switch fabricated on zinc oxide (ZnO) single crystal is presented. High transparent nature of ZnO in visible, near-infrared, mid-infrared and terahertz regions will pave the way for integrated active optics.

Terahertz (THz) radiation generated from photoconductive antenna fabricated on a single crystal zinc oxide (ZnO) is presented. The THz-radiation power is saturated at bias voltages above 800 V/cm and the obtained spectrum extends up to 1 THz. Moreover, ZnO is found to be highly transparent in the visible, near-infrared, mid-infrared and THz frequency regions. The results depicted here will categorically unravel the prospects of using ZnO as a material for integrated active optics. (c) 2005 American Institute of Physics.

Using terahertz transmission spectroscopy, solid-state phase transition onset in an estrogen-like chemical is detected. This is indicated by the observation of two broad absorption peaks and sudden upsurge of terahertz-radiation power at 210 K.

Temperature-dependent absorption-spectra measurements in far-infrared of estrogenic pollutants at various temperatures using terahertz spectroscopy are presented. The shifting of absorption peaks with decreasing temperature is ascribed to the collective vibrational modes of the molecule.

Photonic crystal fiber for terahertz radiation was constructed through highly flexible plastic materials. This fiber is reasonably long, non-polarization changing, and low-loss, consequently we can accomplish preparing long waveguide for terahertz radiation.

Magnetic-field dependences of THz-radiation from InAs and InSb were investigated. For InAs irradiated with 0.8 µm laser, it is found that THz-radiation power exhibits oscillation-like behavior with increasing magnetic field, and reaches maximum at around 3 T. Furthermore, significant enhancement of THz-radiation power is successfully achieved for InSb by using a 1.56 µm exciation and an external magnetic field of 1.2 T.

THz-radiation from femtosecond-laser-irradiated n-type InAs is investigated under the existence of the magnetic field. THz-radiation at around 9 THz is found to be enhanced by using the laser pulses with much shorter duration.