Linewidth reduction in a large-smile laser diode array

We present theory and simulations for a spectral narrowing scheme for laser diode arrays (LDAs) that employs optical feedback from a diffraction grating. We calculate the effect of the so-called smile of the LDA and show that it is possible to reduce the effect by using a cylindrical lens set at an angle to the beam. The scheme is implemented on a 19-element LDA with smile of 7.6 mu m and yields frequency narrowing from a free-running width of 2 to 0.15 nm. The experimental results are in good agreement with the theory. (c) 2005 Optical Society of America.

Distance measurement using the change in junction voltage across a laser diode due to the self-mixing effect

Conventional detection scheme for self-mixing sensors uses an integrated photodiode within the laser package to monitor the self mixing signal. This arrangement can be simplified by directly obtaining the self-mixing signals across the laser diode itself and omitting the photodiode. This work reports on a Vertical-Cavity Surface-Emitting Laser (VCSEL) based selfmixing sensor using the laser junction voltage to obtain the selfmixing signal. We show that the same information can be obtained with only minor changes to the extraction circuitry leading to potential cost saving with reductions in component costs and complexity and significant increase in bandwidth favoring high speed modulation. Experiments using both photo current and voltage detection were carried out and the results obtained show good agreement with the theory.

Effect of high power ultrasound waves on properties of meat: A review

The effect of high power ultrasound waves on physical, biochemical, and microbial properties of meat have been the subject of a great deal of interest in recent years. The present review details the basic principles underlying the effects of ultrasound on the properties of food systems, followed by discussion of specific effects of high power ultrasound on meat products, including muscle, cellular, and subcellular components. In addition, the specific effects of high power ultrasound on the following parameters are discussed: enzyme activities and efficiencies, muscle proteolysis, quality criteria such as tenderness; extraction of protein, gelation, and restructuring of meat products and germicidal properties against meat micro-organisms.