  A novel uni-traveling-carrier photodetector (UTC-PD) structure with an
integrated focusing-reflection (FR) mirror realized by a non-periodic
concentric circular high-contrast grating (NP-CC-HCG), referred to as
FR-UTC-PD, is proposed to enhance responsivity in conventional UTC-PDs. The
FR-UTC-PD allows improving the responsivity by 36.5% at a 1.55-um wavelength as
compared to a UTC-PD without integrated an FR mirror with 84.59% reflectivity.
For 40-um-diameter PDs, the obtained 3-dB bandwidths are unaltered with values
of 18 GHz at -3.0 V bias voltage. The radio-frequency (RF) output power and
photocurrent are -1.77 dBm and 17.56 mA, respectively, at 10 GHz and the -6.0 V
bias voltage.
