Wavelength dispersing device

Abstract

A compact wavelength dispersing device and a wavelength selective optical switch based on the wavelength dispersing device is described. The wavelength dispersing device has a folding mirror that folds the optical path at least three times. A focal length of a focusing coupler of the device is reduced and the NA is increased, while the increased optical aberrations are mitigated by using an optional coma-compensating wedge. A double-pass arrangement for a transmission diffraction grating allows further focal length and overall size reduction due to increased angular dispersion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present invention claims priority from U.S. Provisional Patent Application No. 61 / 071,510, filed May 2, 2008 and U.S. Provisional Patent Application No. 61 / 129,136, filed Jun. 6, 2008, which are incorporated herein by reference.TECHNICAL FIELD[0002]The present invention relates to wavelength dispersing devices, and in particular to free-space optics based compact wavelength dispersing devices for use in wavelength selective optical switches and optical spectrometers.BACKGROUND OF THE INVENTION[0003]A wavelength dispersing device is an optical device for spatially separating spectral components of light for subsequent measurements and, or for further routing or switching of these spectral components.[0004]A wavelength dispersing device is a key component of an apparatus for measuring a spectrum of light, or an optical spectrometer. Optical spectrometers are used for remote sensing of temperature, determining chemical composition and co...

AI Technical Summary

Benefits of technology

[0020]According to another aspect of the present invention, there is further provided a wavelength dispersing device for dispersing a light beam into narrowband sub-beams having focal spots spaced apart along a line of dispersion, comprising:an input port for inputting the light beam;a dispersive unit optically coupled to the input port, for dispersing the light beam into the narrowband sub-beams;a focusing coupler having optical power in a plane containing the line of dispersion, for receiving the spatially separated narrowband sub-beams from the dispersive unit and for focusing them onto the line of dispersion, so that the focal spots of the narrowband sub-beams are disposed along the line of dispersion; anda coma-compensating optical element having two flat optical faces disposed in an optical path between the focusing coupler and the line of dispersion, for compensating coma of the focusing coupler and for reducing an average width of the focal spots along the line of dispersion.

Problems solved by technology

As the beam NA becomes larger, optical aberrations become more problematic.

One drawback of the approach represented by FIG. 3 is that the T-DG 31 creates multiple reflections as a result of the diffraction occurring both in reflection and transmission directions.

As a result of these multiple reflections, multiple stray light beams are created, resulting in deleterious optical cross-talk.

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