Signal beam

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

Unstable resonator optical parametric oscillator based on quasi-phase-matched RbTiOAsO 4

Abstract: We demonstrate improved signal and idler-beam quality of a 3-mm-aperture quasi-phase-matched RbTiOAsO4 optical parametric oscillator through use of a confocal unstable resonator as compared with a plane-parallel resonator. Both oscillators were singly resonant, and the periodically poled RbTiOAsO4 crystal generated a signal at 1.56 µm and an idler at 3.33 µm when pumped at 1.064 µm. We compared the beam quality produced by the 1.2-magnification confocal unstable resonator with the beam quality produced by the plane-parallel resonator by measuring the signal and the idler beam M2 value. We also investigated the effect of pump-beam intensity distribution by comparing the result of a Gaussian and a top-hat intensity profile pump beam. We generated a signal beam of M2 ≈ 7 and an idler beam of M2 ≈ 2.5 through use of an unstable resonator and a Gaussian intensity profile pump beam. This corresponds to an increase of a factor of approximately 2 in beam quality for the signal and a factor of 3 for the idler, compared with the beam quality of the plane-parallel resonator optical parametric oscillator.

Rapid complex mode decomposition of vector beams by common path interferometry

Abstract: We have used common path interferometry for rapid determination of the electric field and complex modal content of vector beams, which have spatially-varying polarization. We combine a reference beam with a signal beam prior to a polarization beam splitter for stable interferograms that preserve intermodal phase shifts even in noisy environments. Interferometric decomposition into optical modes (IDIOM) provides a direct, sensitive measure of the complete electric field, enabling rapid modal decomposition and is ideally suited to single-frequency laser sources. We apply the technique to beams exiting optical fibers that support up to 10 modes. We also use the technique to characterize the fibers by determining a scattering matrix that transforms an input superposition of modes into an output superposition. Furthermore, because interferograms are linear in the field, this technique is very sensitive and can accurately reconstruct beams with signal-to-noise << 1.

Laser controlled optical switching in semiconductors

Abstract: A method and apparatus for switching an infrared radiation signal laser beam in which a semiconductor, capable of transmitting the signal beam without damage, is provided and upon which the signal beam is incident at an angle which may preferably be Brewster's angle. The surface of the semiconductor is irradiated by a second laser beam which has a sufficiently high frequency to produce free carriers in the semiconductor and which has a sufficient radiation intensity and time duration to produce a free carrier density greater than the critical density for the signal beam resulting in substantially total reflection of the signal beam from the semiconductor surface. In particular, a pulsed CO 2 laser beam which is incident on a polycrystalline n-type germanium semiconductor is reflected by irradiating the semiconductor with a pulsed ruby or Nd:glass laser beam.

Robust infrared gratings in photorefractive quantum wells generated by an above‐band‐gap laser

Abstract: Probe beam intensities more than an order of magnitude larger than pump beam intensities do not erase photorefractive gratings during nondegenerate four‐wave mixing in photorefractive GaAs/AlGaAs quantum wells. The pump and probe laser wavelengths are absorbed in spatially separated regions of the multilayer structure. The photoconductivity of a probe beam around 840 nm is confined to the GaAs quantum wells and cannot easily erase the trapped space‐charge gratings in the AlGaAs barriers written by an above‐band‐gap HeNe laser at 633 nm. This allows a weak visible control beam to modulate a strong infrared signal beam.

Waveguide type optical device using large third order non-linearity optical material and method for operating the same

Abstract: Disclosed is a waveguide type optical device utilizing a nonlinear refractive index change according to a large 3rd order nonlinear optical phenomenon. The waveguide type optical device includes a signal beam waveguide through which a signal beam propagates; and a pump beam waveguide through which a pump beam propagates, wherein the pump beam waveguide is disposed adjacent to the signal beam waveguide so that the pump beam can be coupled to the signal beam waveguide, the signal beam waveguide is made of nonlinear optical materials with large 3rd order nonlinear optical property and the pump beam waveguide is made of linear optical materials, and the wavelength range of the signal beam is different from that of the pump beam. By such a structure, the pump beam is coupled to one arm of the signal beam waveguide, thereby generating a 3rd nonlinear phenomenon on one arm of the waveguide through which the signal beam passes. Therefore, the waveguide optical device which implements an all-optical communication device operating as an optical device and can be integrated is provided.