Signal beam

About: Signal beam is a research topic. Over the lifetime, 1881 publications have been published within this topic receiving 20717 citations.

Recording/reproducing method in read-only holographic recording medium, and read-only holographic recording medium

Abstract: A recording signal beam and a recording reference beam are irradiated onto a first surface of a holographic recording medium to write an information as an interference pattern therein. Next, a reflective layer is provided on a second surface opposite to the first surface of the holographic recording medium such that the reflective layer is adhered with the second surface, and a reproducing reference beam is irradiated onto the first surface of the holographic recording medium so as to read a signal beam wh ich is reflected at the reflective layer and reproduced from the holographic recording medium.

Study of laser-induced damage in PPLN

Abstract: Periodically-poled lithium niobate (PPLN) is a well- established nonlinear material for down converting the output from a solid state laser, the pump wavelength, to generate an emission close to 4 micrometers . A simple OPO configuration was used with a resonated signal beam passing through a heated PPLN crystal, to avoid photo-refraction. A Q-switched Nd:YAG pump laser was used for generating short- duration, high-intensity one micron pulses. Direct modulation of the diode sources enable the emission to be controlled. The pump beam had good beam quality, with an M 2 of about 1.8 in each axis, and modulated average power in excess of 6 W. Damage to PPLN crystals used in the solid state laser has been observed. Irreversible damage of the nonlinear medium has been recorded: initially to the output face of PPLN crystals, but latterly to the bulk structure. These observations were made over a range of pumping conditions and OPO configurations. Estimates of the damage threshold have been surprisingly low, of the order of 1.5 J/cm 2 .

Information recording device

Abstract: PURPOSE:To record a high quality two dimensional information hologram on a moving recording medium. CONSTITUTION:Two dimensional information pattern formed by a spatial light modulator 8 is irradiated by parallel beams and diffracted light beams are imaged on the surface of a recording medium surface 11 through a relay lens system 18 and 7. Thus, the image formed on the forming position has the same light wave surface of the diffracted image at the spatial light modulator 8 and the size of the image is recduced to the size decided by the magnification of the system, 18 and 7. That is, the phases of the image formed on the medium 11 are constant over the surface of the medium 11, therefore, the interference image generated by the interference between the above image and a reference beam 10 only include the carrier waves of spatial frequencies only determined by the incident angles of the reference beam 10 and signal beam 9 and no higher order spatial frequency components are inclined. Therefore, if the moving speed of the medium 11 and the spatial frequency of the carrier waves are made compatible, no degradation of higher order spatial frequency components caused by the movement of the medium occurs. Thus, an information recording device is provided with less number of errors in information recording and with a high reliability.

Misalignment Effects in Laser-Induced Grating Experiments.

Abstract: Laser-induced grating spectroscopy (LIGS) is an experimental method in which two pulsed laser beams and a continuous-wave laser beam have to be superimposed under well-defined angles to generate a coherent signal beam. In this Note, the possible effects of different forms of misalignment are examined. This includes the overlap of the pump lasers as well as the influence of the probe laser alignment on the temporal profile of the signal.

Near field broadband PIC processor with improved interference beam

Abstract: A Postbeamformer Interference Canceler (PIC) processes the signals derived from an array of antennas by forming two beams, a signal beam and an interference beam. This paper presents a method to study the performance of the PIC processor using the improved interference beam (IIB) for near field broadband directional sources. The technique presented in this paper extends the idea of previously published paper for far field beamforming to near field broadband beamforming and does not require the steering delays. A number of examples presented show the effectiveness, performance and capability of distance discrimination and robustness of the proposed broadband beamformer and compare with that using PIC with conventional interference beam (CIB) and with that using optimal element space processor (ESP).