Signal beam

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

Coherent optical reception device and coherent optical reception method

Abstract: A coherent optical receiver involves complicated control processing in order to maintain good received signal qualities. Thus, the coherent optical receiver of the present invention has a coherent optical receiver for receiving an input signal beam; an input power monitoring unit for obtaining input power information that is defined on the basis of the power level of the input signal beam; a local oscillator that is connected to the coherent optical receiver; and a control unit that is connected to the coherent optical receiver, the input power monitoring unit, and the local oscillator. The coherent optical receiver is equipped with a 90° hybrid circuit, photoelectric converters, and amplifiers. The input power monitoring unit is placed inside the light path of the input signal beam and in a stage before the amplifiers. The control unit obtains the input power information from the input power monitoring unit and controls the power level of a locally oscillated beam output from the local oscillator on the basis of the input power information.

Phase-sensitive lock-in detection of semiconductor waveguide intensity profiles

Abstract: A phase-sensitive lock-in detection scheme is employed in the measurement of transverse intensity distributions in semiconductor waveguide structures. A modulated (chopped) sampling beam is scanned across the waveguide, and the photocurrent signal from a 1550-nm signal beam in the waveguide is monitored through phase-sensitive lock-in detection (referenced to the sampling beam chopping frequency). It is determined that the photoinjected free-carrier perturbation by the scanning beam can be successfully mapped onto the local signal intensity, and the transverse intensity profile of the signal beam in the waveguide can be extracted. For the 3-μm-wide waveguide and the 2-μm sampling spot size employed in this investigation, the spatial resolution was limited mainly by the 1.7-μm carrier diffusion length in the semiconductor.

Apparatus and method for shifting the frequency of an optical signal by two-stage Raman scattering

Abstract: An apparatus for optically shifting the frequency of an input signal beam includes a first Raman medium that receives an input signal beam, a first pump beam, and a first reference beam to responsively generate an intermediate signal beam comprising a Raman sideband of the first Raman medium. A second Raman medium is optically coupled in series with the first Raman medium. The second Raman medium receives the intermediate signal beam, a second pump beam, and a second reference beam to responsively generate an output signal beam comprising a Raman sideband of the second Raman medium. The generated output signal represents the input signal that is shifted in frequency by a frequency shift that corresponds to the frequency difference between the first and second reference beams.

Experimental study of the angular selectivity of volume phase holograms stored in LiNbO3

Abstract: Changes in the angular Bragg selectivity of volume holograms stored in photorefractive LiNbO3 are analysed for different experimental conditions in the transmission geometry. The effects of the refractive-index-change amplitude, the grating period, the modulation depth, and the wave-front modulation of the signal beam are considered. A very good agreement of the results with the off-Bragg diffraction theory is observed.