Linearized Swept Laser Source for Optical Coherence Analysis System

Abstract

A frequency swept laser source that generates an optical signal that is tuned over a spectral scan band at single discrete wavelengths associated with longitudinal modes of the swept laser source. Laser hopping over discrete single cavity modes allows long laser coherence length even under dynamic very high speed tuning conditions. A ramp drive to the laser is used to linearize laser frequency tuning. A beam splitter is used to divide the optical signal between a reference arm leading to a reference reflector and a sample arm leading to a sample. A detector system detects the optical signal from the reference arm and the sample arm for generating depth profiles and images of the sample.

Description

RELATED APPLICATIONS[0001]This application claims the benefit under 35 USC 119(e) of U.S. Provisional Application No. 60 / 968,185, filed on Aug. 27, 2007.[0002]This application is related to U.S. application No. ______ filed on an even date herewith, entitled Mode Hopping Swept Frequency Laser for FD OCT and Method of Operation, now U.S. Patent Publication No.: ______, which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0003]Optical coherence analysis relies on the use of the interference phenomena between a reference wave and an experimental wave or between two parts of an experimental wave to measure distances and thicknesses, and calculate indices of refraction of a sample. Optical Coherence Tomography (OCT) is one example technology that is used to perform usually high-resolution cross sectional imaging that can provide images of biological tissue structure, for example, on the microscopic scales in real time. Optical waves are sent through an ob...

AI Technical Summary

Benefits of technology

"The invention is a wavelength tuned laser for an optical coherence analysis system. The laser uses a tuning element in a laser cavity that is tuned over a spectral scan band. A ramp generator is used to linearize frequency tuning with time, resulting in a high utilization duty cycle of greater than 50%. The laser can be tuned at very high speeds with fast real-time image frame acquisition and maintains long coherence length. The use of a short laser cavity length with a correspondingly small cavity roundtrip time helps to achieve high tuning speeds. The laser can be discretely tuned over a discrete set of individual wavelengths, which allows for OCT imaging. The invention provides a more efficient and effective laser source for optical coherence analysis."

Problems solved by technology

Simultaneous high speed tuning while maintaining long coherence length is difficult to achieve in conventional tunable lasers, such as conventional external cavity semiconductor tunable lasers.

Such a laser, however, is bulky, has complications related to using very long fiber, and has a number of other limitations.

Such a short required cavity length, e.g. 10 to 30 millimeters (mm), is typically difficult to achieve with conventional external cavity semiconductor lasers.

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