05 Nov 2004
The pick of this week's applications including a tunable VCSEL and a way to measure the thickness of thin films.
• Title: Systems and method for measuring physical, chemical and biological stimuli using vertical cavity surface emitting lasers with integrated tuner
Applicant: Lake Shore Cryotronics, Inc, US
International application number: WO 2004/093272
A tunable vertical-cavity surface-emitting laser (VCSEL) is the basis of a new design of optical sensor described in patent application WO 2004/093272. An integrated MEMS-based mirror placed in front of the emitting surface tunes the laser wavelength. The VCSEL's output beam is then fired down an optical fiber which contains a series of sensors such as Bragg gratings. "The light reflected or transmitted through each sensor is mixed with light passed though an optical reference path and then converted to an electrical signal," say the inventors. "The detected power spectral distribution is indicative of the environmental stimulus on each sensor."
• Title: Method for measuring thin films
Applicant: Koninklijke Philips Electronics, the Netherlands
International application number: WO 2004/092714
Electronics giant Philips has proposed a way to measure the thickness of thin films, specifically metal films with thicknesses of less than 100 angstroms. The method relies on firing an excitation pulse at specific points on the film which causes the air temperature to rise at these locations and acoustic waves to be emitted. "Excited acoustic waves modulate the intensity of a diffracted probe beam resulting in a low frequency component in the signal," explain the authors. "Amplitude of this low-frequency component is correlated with the amount of energy absorbed by the film and with the film thickness."
• Title: Fiber extended semiconductor laser
Applicant: Robert L Thornton, US
International application number: WO 2004/093270
A US inventor is claiming that coupling a VCSEL to an optical fiber can improve the laser's performance. Robert Thornton claims that a fiber-extended cavity VCSEL has high single longitudinal output powers, an extended emission wavelength range and is capable of operating in multiple longitudinal modes. He goes on to say that these properties make VCSELs ideal for applications such as optical communications, quantum key distribution and situations that require the VCSEL to be mode-locked to a predetermined pulse repetition rate.