Optical Emitter With Injection-Locked Lasers for Polarisation Encoding
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Solution Overview
Problem
Existing quantum communication systems face issues with side-channel information leakage and timing errors due to slight variations in laser outputs, which can be exploited by eavesdroppers, and require complex active optical modulators for polarisation encoding.
Innovation Solution
An optical emitter using a primary laser optically injection-locked to multiple secondary lasers, with a polarisation controller to generate optical pulses with varying polarisations, eliminating wavelength distinguishability and reducing temporal jitter, and achieving identical wavelengths without active modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple independent lasers are used to generate optical pulses with different polarisations, then polarisation encoding capability is improved, but wavelength variations cause side-channel information leakage and timing errors
Solution Approach 1:
The system segments the laser functionality into a primary laser that provides the reference wavelength and multiple secondary lasers that generate pulses with different polarisations. Each secondary laser is optically injection-locked to the primary laser, ensuring all lasers operate at the same wavelength while maintaining independent polarisation control capabilities.
Solution Approach 2:
The primary laser acts as an intermediary reference source that mediates the wavelength consistency between multiple secondary lasers. Through optical injection locking, the primary laser's stable wavelength is transferred to all secondary lasers, eliminating wavelength variations without requiring complex active control mechanisms.
2Measurement precision
If active optical modulators are used for polarisation encoding, then polarisation control precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The invention extracts the polarisation control function from complex active optical modulators and implements it directly at the laser source level. By generating pulses with different polarisations from multiple secondary lasers, the system eliminates the need for separate active modulators while maintaining precise polarisation control.
Solution Approach 2:
The secondary lasers self-generate pulses with specific polarisations through the optical injection locking mechanism. Each secondary laser inherently produces light with its characteristic polarisation state, eliminating the need for external active control devices and reducing overall system complexity.
3Adaptability or versatility
If multiple lasers operate independently at different wavelengths, then polarisation encoding flexibility is improved, but detection noise increases due to wavelength distinguishability
Solution Approach 1:
The system creates equipotentiality in wavelength across all lasers through optical injection locking. All secondary lasers are locked to the same reference wavelength from the primary laser, making them wavelength-indistinguishable. This eliminates detection noise while preserving the flexibility to encode different polarisation states.
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 solution provides secure quantum communication by ensuring identical wavelengths and random polarisation changes, reducing detection noise and side-channel information leakage, suitable for high-clock speed systems with simplified, low-cost, and low-power consumption transmitters.
Implementation Method 1
a primary laser and a plurality of secondary lasers, each secondary laser being optically injection locked to said primary laser
Data Source
Figure 1
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Figure 3A~3B
AI summary
An optical emitter comprising a primary laser and a plurality of secondary lasers wherein each secondary laser is optically injection locked to said primary laser, the emitter further comprising at least one polarisation controller configured to control the polarisation of the output of at least one of the secondary lasers, the emitter further comprising a combination unit that is configured to combine the outputs of the secondary laser modules into an output signal.