Optical Science and Engineering ETDs

Publication Date

Summer 7-9-2020


An optical calorimeter for sensitive absorption measurements of non-radiative samples at 4 K was designed, built, and demonstrated. It consists of a cryostat cooled by a commercial pulse tube (PTC) refrigerator, a measurement chamber housing the sample and thermometers, and various fiber-coupled light sources. By employing measures to damp mechanical noise from the environment and active temperature stabilization of critical components of the instrument temperature noise as low as 6 nK/√Hz at 50 mHz was achieved under 15 mW of optical excitation. An optical absorption induced temperature increase of the sample as small as 2.5 nK could be resolved using paramagnetic temperature sensors with SQUID (Superconducting Quantum Interference Device) readout. This resulted in an absorption sensitivity of 0.3 ppm and 0.6 ppb for tunable 30 μW optical excitation from 330 nm to 1700 nm and for 15-mW laser excitation, respectively. The instrument was applied to the characterization of stacks of dielectric films for material science studies and laser mirror development.

Degree Name

Optical Science and Engineering

Level of Degree


First Committee Member (Chair)

Wolfgang Rudolph

Second Committee Member

Stephen T. Boyd

Third Committee Member

Mansoor Sheik-Bahae

Fourth Committee Member

Tito Busani


pico-Watt calorimeter, optical absorption spectroscopy, nK temperature resolution, SQUID, high-resolution thermometry

Document Type