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Signal beam

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


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Patent
Hoon Kim1, Hwang Seong-Teak1
07 Oct 2005
TL;DR: In this article, an optical transmitter using an offset quadrature phase-shift-keying (OQPSK) method is described, which includes a first phase modulator for outputting a first signal beam generated by phase-modulating an input beam based on a first data, a second phase modulators for outputs from a second signal, and a phase delay unit for granting a predetermined phase difference between the first signal and the second signal beam.
Abstract: Disclosed is an optical transmitter using an offset quadrature phase-shift-keying (OQPSK) method. The method includes: a first phase modulator for outputting a first signal beam generated by phase-modulating an input beam based on a first data; a second phase modulator for outputting a second signal beam generated by phase-modulating the input beam based on a second data; a phase delay unit for granting a predetermined phase difference between the first signal beam and the second signal beam; and an optical coupler for coupling the first signal beam and the second signal beam between which the phase difference exists.

10 citations

Proceedings ArticleDOI
28 May 1999
TL;DR: In this paper, the authors used dynamic holography in a photorefractive material to combine a distorted signal beam with a plane-wave reference beam and match their wavefronts for homodyne detection.
Abstract: Summary form only given. Laser-based ultrasound is a promising technique for remote ultrasonic inspection. One approach for the measurement of small ultrasonic surface displacements uses dynamic holography in a photorefractive material to combine a distorted signal beam with a plane-wave reference beam and match their wavefronts for homodyne detection. Slow variations in the wavefront of the signal beam are compensated by the real-time hologram and thus do not produce noise or interfere with the quality of the wavefront overlap in the output beams.

10 citations

Journal ArticleDOI
TL;DR: In this paper, the slowing down of light in Ce:BaTiO3 at room temperature via degenerate two-wave mixing for chopped pulses is reported, and the effect of pulse width of signal beam and pump intensity on the slowing-down action in the crystal is studied.
Abstract: The slowing down of light in Ce:BaTiO3 at room temperature via degenerate two-wave mixing for chopped pulses is reported. Delay of 0.9 ms is observed for chopped pulses of duration 8 ms, corresponding to a group velocity of 5.5 m/s. Effect of pulse width of signal beam and pump intensity onto the slowing down action of light in the crystal is studied. The building up and decay time of photo grating is also recorded as a function of pump beam intensity.

10 citations

Journal ArticleDOI
TL;DR: A new method of measuring a water-stimulated Brillouin scattering (SBS) frequency shift by optical coherent detection is presented, in order to remote-sense the underwater temperature of the ocean.
Abstract: In this paper, a new method of measuring a water-stimulated Brillouin scattering (SBS) frequency shift by optical coherent detection is presented, in order to remote-sense the underwater temperature of the ocean. A single longitudinal mode, passively Q-switched pulsed Nd:YAG laser is used as the light source, the water SBS beam is used as the signal beam, and a portion of the incident laser beam is used as the local oscillator. The heterodyne is detected by a high-speed photodetector, and the heterodyne frequency is the Brillouin frequency shift. Therefore, the underwater temperature can be determined according to the relationship between the Brillouin frequency shift and the water temperature. To test and verify its practicability, the heterodyne waveforms at different water temperatures are recorded in the laboratory with a wide-band oscilloscope, and the Brillouin frequency shifts are deduced by a Fourier transform. The experimental results are consistent with the theoretical analysis. This work provides the foundation for the development of a water temperature measurement system based on coherent Brillouin scattering.

10 citations

Journal ArticleDOI
10 May 2009-Pramana
TL;DR: In this article, the steady-state amplification of light beam during two-wave mixing in photorefractive materials has been analyzed in the strong nonlinear regime and the oscillation conditions for unidirectional ring resonator have been studied.
Abstract: The steady-state amplification of light beam during two-wave mixing in photorefractive materials has been analysed in the strong nonlinear regime. The oscillation conditions for unidirectional ring resonator have been studied. The signal beam can be amplified in the presence of material absorption, provided the gain due to the beam coupling is large enough to overcome the cavity losses. Such amplification is responsible for the oscillations. The gain bandwidth is only a few Hz. In spite of such an extremely narrow bandwidth, unidirectional oscillation can be observed easily at any cavity length in ring resonators by using photorefractive crystals as the medium and this can be explained in terms of the photorefractive phase-shift. The presence of such a phase-shift allows the possibility of the non-reciprocal steady-state transfer of energy between the two light beams. Dependence of gain bandwidth on coupling constant, absorption coefficient of the material’s cavity length (crystal length) and modulation ratio have also been studied.

10 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202310
202215
202131
202040
201929
201844