33 research outputs found
Effect of atomic layer deposition on the quality factor of silicon nanobeam cavities
In this work we study the effect of thin-film deposition on the quality factor (Q) of silicon nanobeam cavities. We observe an average increase in the Q of 38±31% in one sample and investigate the dependence of this increase on the initial nanobeam hole sizes. We note that this process can be used to modify cavities that have larger than optimal hole sizes following fabrication. Additionally, the technique allows the tuning of the cavity mode wavelength and the incorporation of new materials, without significantly degrading Q
Arrays of Ag split-ring resonators coupled to InGaAs single-quantum-well gain
We study arrays of silver split-ring resonators operating at around
1.5-{\mu}m wavelength coupled to an MBE-grown single 12.7-nm thin InGaAs
quantum well separated only 4.8 nm from the wafer surface. The samples are held
at liquid-helium temperature and are pumped by intense femtosecond optical
pulses at 0.81-{\mu}m center wavelength in a pump-probe geometry. We observe
much larger relative transmittance changes (up to about 8%) on the
split-ring-resonator arrays as compared to the bare quantum well (not more than
1-2%). We also observe a much more rapid temporal decay component of the
differential transmittance signal of 15 ps for the case of split-ring
resonators coupled to the quantum well compared to the case of the bare quantum
well, where we find about 0.7 ns. The latter observation is ascribed to the
Purcell effect that arises from the evanescent coupling of the split-ring
resonators to the quantum-well gain. All experimental results are compared with
a recently introduced analytical toy model that accounts for this evanescent
coupling, leading to excellent overall qualitative agreement
Interference filters as nonlinear decision-making elements for three-spot pattern recognition and associative memories
Simple patterns consisting of three spots (V and Γ) have been recognized by dividing, shifting, and recombining
beams onto bistable ZnS interference filters. This experiment demonstrates AND-gate operation,
cascading, and a moderate amount of parallelism, but a laser power of several watts was required and the
response times were several milliseconds. An associative memory for fingerprint identification has been
constructed using a VanderLugt correlator and an interference filter as a reflective thresholding device