Quantum-Dot O-Band U-Comb Laser With Tunable Mode Spacing
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Solution Overview
Problem
Existing comb lasers face challenges such as limited power uniformity, bandwidth, and mode stability, particularly in achieving tunable or flexible mode spacing suitable for wide-ranging applications like WDM communications.
Innovation Solution
The development of an optical source with a semiconductor laser chip featuring multiple epitaxial gain layers, which provides multiple lasing wavelengths in a band without mode hopping and with reduced mode beating, utilizing an optical component like an aperiodic grating or ring resonators to select laser modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mode locked lasers are used to generate frequency combs, then the comb spacing is defined by the optical cavity length, but the power uniformity per line and bandwidth are limited due to optical cavity dispersion
Solution Approach 1:
The patent extracts the optical cavity from the comb laser system, using an external cavity design where the gain chip is coupled to a separate external optical cavity. This separation allows independent optimization of the gain medium and the cavity dispersion characteristics, eliminating the limitation where cavity dispersion restricts bandwidth and power uniformity.
Solution Approach 2:
The patent implements dynamic tuning capability by making the external cavity length adjustable. This allows the comb spacing to be dynamically reconfigured without changing the gain chip, enabling flexible adaptation to different application requirements while maintaining stable operation.
2Quantity of substance
If optical fiber-based parametric amplifier comb lasers are used, then large bandwidths and tunability are achieved, but the efficiency of optical pumping and compactness are insufficient for data center applications
Solution Approach 1:
The patent replaces the optical fiber-based parametric amplification mechanism with a semiconductor gain chip-based direct lasing approach. This substitution eliminates the need for optical pumping of parametric processes, achieving higher optical-to-optical efficiency while maintaining large bandwidth through the external cavity design.
Solution Approach 2:
The patent integrates the semiconductor gain chip into an external optical cavity, creating a nested structure where the gain medium is coupled to a larger cavity system. This allows the compact gain chip to benefit from the large mode spacing and low dispersion characteristics of the external cavity, combining compactness with high performance.
3Adaptability or versatility
If AWG lasers are used with multiple gain sections, then each wavelength can be addressable by its own gain section, but the grid spacing is fixed by the AWG and tuning is not efficient
Solution Approach 1:
The patent implements a dynamically tunable external cavity design where the cavity length can be adjusted to change the mode spacing. This allows the laser to adapt to different wavelength grids and spacing requirements, providing flexibility that fixed AWG-based systems cannot achieve.
Solution Approach 2:
The patent creates a universal comb laser platform that can be configured for different applications by adjusting the external cavity parameters. A single device can serve multiple functions across different wavelength ranges and spacing requirements, eliminating the need for application-specific fixed-grid designs.
4Quantity of substance
If Vernier ring comb lasers are used, then each wavelength is addressable by its own gain section with uniform power balancing, but the device complexity increases and the grid spacing is constrained by the ring resonator design
Solution Approach 1:
The patent segments the optical cavity into an external cavity portion and a gain chip portion, allowing independent optimization. The external cavity provides the mode structure and spacing, while the gain chip provides uniform gain across all modes, achieving power uniformity without requiring multiple separate gain sections.
Solution Approach 2:
The external optical cavity acts as an intermediary between the gain chip and the output, mediating the mode structure and spacing. This intermediary allows the simple gain chip to produce uniform power across multiple wavelengths by providing the cavity feedback that distributes power evenly among the comb lines.
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 enables an efficient, tunable, and flexible comb laser source with multiple-wavelength output channels and wide wavelength separation, exceeding requirements for communications lasers at high data rates, and addressing technical and cost bottlenecks in various applications.
Implementation Method 1
a gain medium that provides multiple lasing wavelengths in a band of wavelengths
Implementation Method 2
an optical cavity that includes at least one mirror
Implementation Method 3
an optical component that selects laser modes of the optical cavity, where the optical component includes: an aperiodic grating; an echelle grating
Implementation Method 4
a set of ring resonators that provide the lasing wavelengths
Data Source
AI summary
An optical source is described. This optical source may include a semiconductor laser chip and a silicon-photonics chip that provide an optical cavity. The semiconductor laser chip may provide gain at multiple lasing wavelengths in a band of wavelengths. Moreover, the silicon-photonics chip may adjust a size of an optical signal proximate to an interface between the semiconductor laser chip and the silicon-photonics chip. Furthermore, by adjusting a phase of a phase shifter and resonance frequencies of a micro-ring resonator in the silicon-photonics chip, a center frequency of a passband of the micro-ring resonator may be matched to a non-zero integer multiple of a cavity-mode spacing. This may allow the optical source to mode-lock the lasing wavelengths of the optical source by suppressing unwanted lasing wavelengths and re-enforcing the lasing wavelengths. In some embodiments, a free-spectral range of the optical source may be between 100 GHz and 800 GHz.