Patent ID: 7130320

Claim:
A rotary tuning element, comprising: a variable transmission filter, having a transmission wavelength that varies as a function of rotation angle; a compensation prism having a thickness that varies as a function of rotation angle, the compensation prism usable to alter a cavity length of an external cavity laser to correspond to the transmission wavelength of the variable transmission filter; a first etalon having a transmission wavelength that varies as a function of rotation angle in a manner that corresponds to the transmission wavelength of the variable transmission filter; and a second etalon having a transmission wavelength that varies as a function of rotation angle in a manner that corresponds to the transmission wavelength of the variable transmission filter, wherein: the first and second etalon are arranged in series along a nominal optical path through the rotary tuning element; and the variable transmission filter, the compensation prism, and the first and second etalons are arranged such that the rotary tuning element is usable to provide nominally mode-hop free tuning when positioned along an optical path of an external cavity laser.