Temperature compensated optical device

Abstract

A temperature compensated optical device includes a compression-tuned glass element having a Bragg grating therein, a compensating material spacer and an end cap all held within an outer shell The element end cap and shell are made of a material having a low coefficient of thermal expansion (CTE), e.g., silica, quartz, etc. and the spacer is made of a material having a higher CTE, e.g., metal, Pyrex®, ceramic, etc. The material and length L of the spacer is selected to offset the upward grating wavelength shift due to temperature. As temperature rises, the spacer expands faster than the silica structure causing a compressive strain to be exerted on the element which shifts the wavelength of the grating down to balance the intrinsic temperature induces wavelength shift up. As a result, the grating wavelength is substantially unchanged over a wide temperature range. The element includes either an optical fiber having at least one Bragg grating impressed therein encased within and fused to at least a portion of a glass capillary tube or a large diameter waveguide (or cane) with a grating having a core and a wide cladding, which does not buckle over a large range of compressive axial strains. The element may have a “dogbone” shape to amplify compressive strain on the grating The device may also be placed in an axially tunable system that allows the wavelength to be dynamically tuned while remaining athermal. In addition to a grating, the device may be an athermal laser, DFB laser, etc. Also, the entire device may be all made of monolithic glass materials.