New resonant cavity-enhanced absorber structures for mid-infrared detector applications

Abstract

A new dielectric Fabry-Perot cavity was designed for a resonant enhancing optical absorption by a thin absorber layer embedded into the cavity. In this cavity, the front mirror is a subwavelength grating with ∼ 100% retroreflection. For a HgCdTe absorber in a matching cavity of the new type, the design is shown to meet the combined challenges of increasing the absorbing efficiency of the entire device up to ∼ 100 % and reducing its size and overall complexity, compared to a conventional resonant cavity enhanced HgCdTe absorber, while maintaining a fairly good tolerance against the grating's fabrication errors.Keywords Optical resonant cavity · Photodetectors · HgCdTe · Gratings Here λ 0 is a resonance wavelength n c and t c is the refractive index (RI) and length of the FP cavity, respectively, ϕ f and ϕ b are the reflection phase of the mirror that

Upmost efficiency, few-micron-sized midwave infrared HgCdTe photodetectors

“…Therein, for manufacturing such devices needs only few layer deposition steps, the grating fabrication accuracy is most critical. Hitherto testing the sensitivity of the η spectra of the designed one-GLS mirror RCE PDs to changes in the grating's etch depth and width around the design values, we found 12,13 ones with tolerances certainly practical from the current micro-fabrication status viewpoint.…”

“…In a quest for thinning PDs, we proposed to replace the front DBR mirror by an one-dimensional (1D) gratingon-layer structure (GLS), and reported the proof-of-concept examples of HgCdTe based PDs 12,13 . The roundtrip phase control 1 extended to the presence of GLS and optimization allowed us 12,13 to achieve tolerant designs with the η ≈ 100% and backside DBR twice as thin as compared to those of an optimized conventional RCE PD comprising the same materials.…”

“…In a quest for thinning PDs, we proposed to replace the front DBR mirror by an one-dimensional (1D) gratingon-layer structure (GLS), and reported the proof-of-concept examples of HgCdTe based PDs 12,13 . The roundtrip phase control 1 extended to the presence of GLS and optimization allowed us 12,13 to achieve tolerant designs with the η ≈ 100% and backside DBR twice as thin as compared to those of an optimized conventional RCE PD comprising the same materials. Still, if the back mirror remains to be a DBR one the RCE device can not be downscaled anymore due to lower bounds imposed on the cavity and DBRs thicknesses by tailoring the round-trip phase and DBR mirrors' reflectance, respectively 1,2 .…”

“…Here, to meet challenge of further reducing the size and complexity of the entire PD device by surpassing the above thickness bounds while benefiting from our previous designs 12,13 which attained uppermost η, we propose to replace the back DBR mirror in those designs also by an 1D GLS with the same grating period as that in the front one. High refractive index (RI) contrast GLSs are attracting much interest 16 as a new platform for integrated optoelectronics due to their ability to function in some spectral range quite alike usual optical elements, e.g.…”

Ultrathin high efficiency photodetectors based on subwavelength grating and near-field enhanced absorption

“…[2][3][4], but for technological reasons RCE PDs for visible and infrared (IR) prove rather thick. [2][3][4][5] As a first step to thinner RCE PDs, we proposed to replace one DBR by a grating-on-layer mirror and reported 5,6 proof of the concept examples of HgCdTe based PDs for mid IR. Round-trip phase control 1 and optimization allowed us to achieve tolerant designs with much higher η and the second DBR half as thick compared to those of an optimized conventional RCE PD comprising the same materials.…”