Segmented Grating Laser for Narrow Linewidth Noise Suppression
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Solution Overview
Problem
Current semiconductor lasers have linewidths greater than 100 kHz, which limits the performance of optical sensors, and achieving narrow linewidths with external cavities results in complex and unstable assemblies unsuitable for sensor applications.
Innovation Solution
A semiconductor laser design featuring a grating along the cavity with multiple waveguide sections of varying ridge/mesa width and contact electrodes for active feedback noise suppression, enabling non-uniform current distribution and localized modulation to achieve narrow linewidths without mode-hopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a semiconductor laser is combined with an external cavity to achieve narrow linewidth, then the laser linewidth is reduced, but the assembly becomes complex and loses the size advantages of semiconductor lasers
Solution Approach 1:
The laser cavity is segmented into multiple waveguide sections with different ridge widths, allowing independent current control for each section. This segmentation enables distributed feedback control throughout the cavity, achieving narrow linewidth without requiring an external cavity assembly.
Solution Approach 2:
The grating structure is integrated directly within the semiconductor laser waveguide, nesting the feedback mechanism inside the laser itself rather than requiring an external cavity. This nested configuration maintains the compact size of semiconductor lasers while providing the feedback necessary for narrow linewidth operation.
2Manufacturing precision
If a semiconductor laser is combined with an external cavity to achieve narrow linewidth, then the laser linewidth is reduced, but the laser becomes susceptible to mode-hopping and unstable
Solution Approach 1:
Multiple contact electrodes are positioned at different locations along the laser cavity to provide distributed feedback control. This feedback mechanism actively suppresses wavelength and frequency drifts, preventing mode-hopping and maintaining laser stability while achieving narrow linewidth.
Solution Approach 2:
Different sections of the laser cavity have different ridge widths optimized for their specific functions: some sections are optimized for gain, others for feedback, and others for mode control. This local optimization of properties throughout the cavity enhances overall laser stability and prevents mode-hopping.
3Reliability
If active feedback is used to modulate bias current to suppress wavelength drift, then low frequency stability is improved, but the frequency modulation response changes sign at a few hundred kilohertz limiting high frequency suppression
Solution Approach 1:
The laser cavity is divided into multiple independently controllable sections with separate contact electrodes. This segmentation allows different frequency components of wavelength drift to be suppressed by modulating the bias current in different sections, extending the effective feedback frequency range beyond the limitation of single-section feedback.
Solution Approach 2:
The feedback control is extended from a single-dimensional (single contact) approach to a multi-dimensional (multiple contacts at different positions) approach. This additional spatial dimension in the feedback control enables suppression of a broader frequency range by distributing the feedback action across multiple locations in the cavity.
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 design achieves narrow linewidths up to very high frequencies, reduces frequency noise, and maintains stability, making it suitable for next-generation optical sensor applications.
Implementation Method 1
each of the plurality of waveguide sections having a ridge/mesa width for detuning the grating in each of the plurality of grating sections
Implementation Method 2
the plurality of contact electrodes for applying a different current to each of the plurality of waveguide sections to enable active feedback noise suppression
Implementation Method 3
a mesa/ridge with a varying width to detune grating sections and compensate for the effects of longitudinal spatial hole burning, of the carrier density distribution due to injection levels
Implementation Method 4
a BH laser structure to further reduce the frequency noise
Data Source
AI summary
A laser comprising a narrow linewidth, comprising: a grating along a laser cavity; a laser waveguide having a plurality of waveguide sections corresponding to a plurality of grating sections, each of the plurality of waveguide sections having a ridge/mesa width for detuning the grating in each of the plurality of grating sections; and a plurality of contact electrodes contacting each of the plurality of waveguide sections, the plurality of contact electrodes for applying a different current to each of the plurality of waveguide sections to enable active feedback noise suppression.