  Spectral pattern recognition is used to measure temperature and generate
calibrated wavelength/frequency combs using a single silicon waveguide ring
resonator. The ring generates two incommensurate interleaving TE and TM
spectral combs that shift independently with temperature to create a spectral
pattern that is unique at every temperature. Following an initial calibration,
the ring temperature can be determined by recognizing the spectral resonance
pattern, and as a consequence the wavelength of every resonance is also known.
Two methods of pattern based temperature retrieval are presented. In the first
method, the ring is locked to a previously determined temperature set-point
defined by the coincidence of only two specific TE and TM cavity modes. Based
on a prior calibration at the set-point, the ring temperature and hence all
resonance wavelengths are then known and the resulting comb can be used as a
wavelength calibration reference. In this configuration, all reference comb
wavelengths have been reproduced within a 5 pm accuracy across an 80 nm range
by using an on-chip micro-heater to tune the ring. For more general photonic
thermometry, a spectral correlation algorithm is developed to recognize a
resonance pattern across a 30 nm wide spectral window and thereby determine
ring temperature continuously to 50 mK accuracy. The correlation method is
extended to simultaneously determine temperature and to identify and correct
for wavelength calibration errors in the interrogating light source. The
temperature and comb wavelength accuracy is limited primarily by the linewidth
of the ring resonances, with accuracy and resolution scaling with the ring
quality factor.
