Waveguide Photodetector With Tuned Reflector for High SNR
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Solution Overview
Problem
Current optical communication systems face challenges in achieving high signal-to-noise ratio (SNR) and sensitivity while maintaining a compact footprint and low power consumption, particularly in effectively filtering and absorbing specific frequency bands of optical signals.
Innovation Solution
The implementation of a waveguide photodetector system with a high absorption coefficient material and a reflector tuned to reflect a specific frequency band of interest, allowing the frequency band to propagate through multiple paths while rejecting other frequencies, thereby increasing the effective absorption distance and SNR of the desired frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a waveguide photodetector uses a material with high absorption coefficient, then the absorption efficiency is improved, but the device length must be increased to achieve greater absorption, which increases the device footprint
Solution Approach 1:
The patent implements a periodic structure using distributed Bragg reflectors (DBRs) that create multiple reflections of light within the waveguide photodetector. This periodic action allows photons to interact with the absorption material multiple times, significantly enhancing absorption efficiency without requiring a proportional increase in device length. The DBRs create a resonant cavity effect that traps and recirculates light through the active region.
Solution Approach 2:
The patent introduces a vertical dimension to light propagation by implementing omnidirectional reflectors that reflect light in multiple directions (upward, downward, and sideways) within the waveguide structure. This multi-dimensional light trapping allows the photodetector to achieve high absorption efficiency in a compact footprint by utilizing the vertical dimension rather than solely extending the horizontal length.
2Area of stationary object
If the waveguide photodetector is designed to be compact, then the footprint is reduced, but the absorption distance is limited, reducing the signal-to-noise ratio
Solution Approach 1:
The periodic DBR structure creates multiple passes of light through the absorption region, effectively increasing the absorption distance within a compact footprint. Each reflection off the DBRs provides additional interaction length, accumulating absorption效果 without extending the physical device dimensions, thereby maintaining high signal-to-noise ratio in a compact form factor.
Solution Approach 2:
By utilizing vertical and lateral reflections within the waveguide, the patent effectively multiplies the absorption path length in three-dimensional space. This allows the compact device to achieve equivalent absorption to much longer linear structures by exploiting the volumetric light-trapping capability of the omnidirectional reflectors.
3Device complexity
If traditional photodetectors are used without frequency tuning, then the device structure is simple, but the ability to filter specific frequency bands and reject noise is limited
Solution Approach 1:
The distributed Bragg reflectors create a periodic optical structure with specific refractive index variations that are tuned to reflect specific wavelength bands. This periodic structure acts as a built-in frequency filter, allowing the photodetector to selectively absorb desired frequency bands while reflecting noise frequencies, achieving high frequency selectivity through the periodic optical path.
Solution Approach 2:
The patent tunes the optical parameters of the DBRs by adjusting the thickness, refractive index, and period of the alternating layers to match specific wavelength bands of interest. This parameter optimization allows the reflectors to be precisely tuned for frequency-selective operation, enabling the photodetector to target specific communication wavelengths while rejecting out-of-band noise and interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances responsivity and sensitivity by increasing the signal-to-noise ratio of the output signal, providing improved performance in a compact and low-power consumption design, effective for a wider range of frequencies compared to traditional systems.
Implementation Method 1
a reflector that is tuned to reflect a frequency band of interest
Implementation Method 2
a waveguide photodetector that can absorb photons associated with the optical signal propagating through a waveguide therein, such as via a material that has a high absorption coefficient
Implementation Method 3
at least one photodetector for converting the optical signal to an electric signal
Implementation Method 4
a waveguide photodetector that can absorb photons associated with the optical signal propagating through a waveguide therein
Data Source
AI summary
One example includes a photodetector system. The system includes a waveguide photodetector into which an input optical signal comprising a frequency band of interest is provided and from which the input optical signal is absorbed to generate an output signal that is indicative of an intensity of the input optical signal. The system also includes a reflector coupled to the waveguide photodetector and which is to reject frequencies outside of the frequency band of interest and to reflect the frequency band of interest back into the waveguide photodetector.