Optical Amplifier Array with Photonic Crystal Spontaneous Emission Suppression
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Solution Overview
Problem
Low light level imaging systems, such as those used in night vision applications, face challenges in ultra-low light conditions where few photons per pixel arrive, leading to grainy or unusable images due to noise from dark current and digital readout circuitry, often resulting in no image capture at all.
Innovation Solution
An optical amplifier system utilizing semiconductor active regions embedded within photonic crystals with an electromagnetic band gap that suppresses spontaneous emission, amplifying light with low noise by aligning the conduction band edge energy with the photonic band gap energy, and using a crossbar or stacked arrangement of input, intermediary, and output optical amplifiers to enhance light amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional FPA detectors are used in ultra-low light conditions, then the device structure is simple, but the image quality becomes grainy or unusable due to noise from dark current and digital readout circuitry
Solution Approach 1:
An optical amplifier is introduced as an intermediary component between the optical input and the FPA detector. This amplifier boosts the weak optical signal before detection, making the photon signal stronger than the inherent noise from dark current and readout circuitry, thereby enabling usable image capture in ultra-low light conditions
Solution Approach 2:
The optical amplifier performs preliminary amplification of the optical signal before it reaches the detector. By amplifying the signal in advance, the system ensures that the signal-to-noise ratio is sufficient for quality image detection, preventing the signal from being overwhelmed by subsequent noise in the detection chain
2Measurement precision
If optical amplifiers are used to amplify weak optical signals, then the signal-to-noise ratio improves, but spontaneous emission from the semiconductor active region adds noise to the amplified signal
Solution Approach 1:
The photonic crystal structure is designed with specific local properties - a photonic bandgap at the wavelength corresponding to the semiconductor's spontaneous emission. This local modification of the electromagnetic environment at the specific location and wavelength of the active region suppresses spontaneous emission without affecting the amplification of the desired optical signal
Solution Approach 2:
The system changes the photonic environment parameter by introducing a photonic crystal with a tailored bandgap. This parameter change selectively inhibits spontaneous emission at the emission wavelength while maintaining transparency for the signal wavelength, thereby reducing noise without compromising signal amplification
3Power
If multiple optical amplifiers are arranged in crossbar or stacked configuration, then light amplification is enhanced, but the device complexity increases
Solution Approach 1:
Multiple optical amplifiers are merged into a single integrated optical component with input, intermediary, and output amplifier regions combined in one structure. This merging achieves enhanced light amplification through the combined action of multiple amplifier regions while reducing the overall device complexity by eliminating the need for separate discrete amplifier components and their interconnections
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
The system effectively amplifies low light levels with minimal noise, enabling clear image capture in ultra-low light conditions by suppressing spontaneous emission and providing amplified light to optical detectors, thereby improving imaging quality in night vision and other low-light applications.
Implementation Method 1
The semiconductor active region is embedded within a photonic crystal having an electromagnetic band gap having photon energies overlapping the energy of the conduction band edge of the electronic band gap such that spontaneous emission of photons in the semiconductor active region is suppressed
Implementation Method 2
The intermediary switchable optical amplifiers when switched on amplify light from the optical inputs
Data Source
AI summary
An optical system is described. The optical system has an optical amplifier array. The optical amplifier array has an array of optical amplifiers. Each optical amplifier has an optical amplifier region including a semiconductor active region having a direct electronic band gap with a conduction band edge. The semiconductor active region is embedded within a photonic crystal having an electromagnetic band gap having photon energies overlapping the energy of the conduction band edge of the electronic band gap such that spontaneous emission of photons in the semiconductor active region is suppressed.