A method comprising generating an optical beam with a laser, filtering the optical beam to select a desired wavelength with an etalon positioned in a path of the optical beam, heating the etalon to an operational temperature using a heater, monitoring the operational temperature of the etalon with a resistive thermal device disposed in or on a thermally conductive frame bonded to the etalon, and applying feedback control of the heater based on the monitoring to select the desired wavelength.