Method and apparatus for adjusting the wavelength in an optical device and laser using the method

Abstract

In a method and a corresponding apparatus for adjusting the wavelength in an optical device, a wavelength selective filter element, for example a Fabry-Perot etalon, whose wavelength characteristic depends on the angle of incidence (.alpha..sub.min) of the light beam on the filter element is arranged on a shaft which can be rotated by a motor. The filter element is mounted to the shaft such that its surface normal forms an angle (.gamma..sub.o) with the axis. The shaft itself is inclined relative to the axis of the light beam passing through the filter element. When the axis is rotating, the angle of incidence of the light beam on the filter element changes, resulting in a change of the wavelength of the transmitted beam. By rotating the axis, very small changes of the angle of incidence and thus of the wavelength can be precisely adjusted. The invention can be used in an external cavity laser comprising a semiconductor laser chip, a lens and a grating. Rotation of the grating by a drive unit provides for coarse tuning of the output wavelength of the external cavity laser and rotation of the filter element provides for fine tuning.

Dependencies are inferred from the claim text.