Pulse-Interference Emitter for Low-Power Polarization Encoding
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Solution Overview
Problem
Existing quantum communication systems face challenges in efficiently encoding information on single photons using phase and amplitude modulation without the need for complex and power-hungry external modulators, particularly in high-clock-rate applications like quantum key distribution (QKD) and free-space QKD.
Innovation Solution
An emitter is designed to utilize the interference of pulses with different fixed polarizations and phases, converting a sequence of phase-encoded pulses into a sequence of polarization-encoded pulses without the use of active polarization modulators, using gain-switched lasers and optical injection locking to achieve controlled phase differences between pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external modulators are used for phase and amplitude modulation, then information encoding capability is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent combines the phase modulation and amplitude modulation functions into a single integrated modulator that simultaneously performs both operations on the optical signal. This merging of functions eliminates the need for separate external modulators, thereby reducing device complexity while maintaining full information encoding capability through combined phase and amplitude modulation.
Solution Approach 2:
The integrated modulator is designed to perform multiple functions - both phase modulation and amplitude modulation - within a single device component. This multi-functionality allows the system to achieve complex information encoding without requiring multiple specialized modulators, thus simplifying the overall emitter design while preserving versatility.
2Adaptability or versatility
If external modulators are used for phase and amplitude modulation, then information encoding capability is improved, but power consumption increases
Solution Approach 1:
By merging phase modulation and amplitude modulation into a single integrated modulator, the patent reduces the total power consumption compared to using separate external modulators. The combined device operates more efficiently by performing both modulation functions simultaneously, thereby maintaining full information encoding capability while lowering the overall energy requirement of the emitter system.
3Device complexity
If the emitter is simplified to be compact and low-power, then ease of manufacture and operation are improved, but information encoding capability may be reduced
Solution Approach 1:
The patent employs parameter changes within the integrated modulator to achieve both phase and amplitude modulation through a single device. By dynamically adjusting operational parameters such as modulation depth, frequency, and phase shift, the simplified emitter maintains full information encoding capability while remaining compact and low-power, thus resolving the contradiction between simplicity and versatility.
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 approach simplifies the emitter design, making it compact, low-cost, and low-power, suitable for high-clock-rate optical communications and QKD systems, including polarisation-encoding quantum key distribution and free-space QKD, while ensuring secure information encoding.
Implementation Method 1
The primary laser is configured to output a sequence of optical pulses... using gain-switched lasers and optical injection locking to achieve controlled phase differences between pulses
Implementation Method 2
using gain-switched lasers and optical injection locking to achieve controlled phase differences between pulses
Implementation Method 3
An emitter is designed to utilize the interference of pulses with different fixed polarizations and phases, converting a sequence of phase-encoded pulses into a sequence of polarization-encoded pulses
Data Source
Figure 1A~4C
Figure 2A~2D
Figure 3A~3B
AI summary
An emitter configured to output a sequence of periodic light pulses with different polarisations, the emitter comprising: a beam splitter configured to divide the pulses of a first sequence of pulses, such that each pulse is split between a first path and a second path, the first sequence of pulses having a varying phase and a first polarisation; a polarisation rotator configured to rotate the polarisation state of pulses in one of the first path or the second path with respect to the polarisation state of pulses in the other path; a time delay component configured to provide a time delay such that the first sequence of pulses in the first arm are delayed by one period with respect to the first sequence of pulses in the second arm; an optical combination component configured to combine the delayed first sequence of pulses from the first path with the first sequence of pulses from the second path to produce an output sequence of pulses where each pulse in the output sequence is a combination of a pulse from the second path and a delayed pulse from the first path and has a polarisation determined from the phase difference between combined pulses and the polarisation of the first path and the second path.