Methods and apparatuses for measuring optical radiation

An optical detector, comprising:

• a controller;
• a pump laser generator constructed to generate a modulated pump laser;
• a probe laser generator constructed to generate a probe laser;
• a microring cavity constructed to receive the probe laser and the pump laser, wherein the microring cavity includes a covered portion and an exposed portion;
• a microbridge suspended above the exposed portion of the microring cavity so as to interact with an evanescent optical field in the exposed portion of the microring,
• wherein the controller is configured to control the wavelength and modulated power of the pump laser such that the pump laser generates the evanescent optical field that excites the microbridge to a mechanical resonance frequency,
• wherein the microbridge is constructed to absorb radiation from light impinging on the microbridge such that a resonance frequency of the microbridge changes in proportion to an amount of absorbed radiation, and
• wherein the probe laser is configured to be modulated by the microbridge in proportion to a vibration amplitude of the microbridge to form a modulated probe laser;
• and
• a photodetector constructed to receive the modulated probe laser and generate data based thereon,
• wherein the controller is constructed to receive the data from the photodetector, determine a change in resonance frequency of the microbridge, and calculate an amount of absorbed radiation from the change in resonance frequency of the microbridge.