Stacked Diode Laser Module for Tunable Narrow-Linewidth Power
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Solution Overview
Problem
Current tunable narrow spectral width high power semiconductor laser systems face limitations in output power and wavelength adjustability, particularly in systems using a single laser diode with an external resonant cavity and volumetric holographic grating, which restrict their application in high-power scenarios.
Innovation Solution
A semiconductor laser module with N laser diodes, equipped with fast- and slow-axis collimators and reflective mirrors, combined with an optical system comprising cylindrical lenses, a half-wave plate, and a transmission grating, allows for beam expansion or reduction to achieve narrow spectral width and wavelength tuning through adjustments of mirror angles and distances between lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single laser diode with external resonant cavity and volumetric holographic grating is used, then narrow spectral width is achieved, but output power is low
Solution Approach 1:
The system divides the laser source into multiple laser diodes (at least two) that are spatially separated and stacked along the fast-axis direction. Each laser diode operates independently to generate laser beams with specific wavelengths, achieving both high power through combination and narrow spectral width through individual wavelength control and grating-based feedback.
2Measurement precision
If volumetric holographic grating is used in external resonant cavity, then spectral width is narrowed, but wavelength adjustability is limited
Solution Approach 1:
The system employs dynamic control elements including a half-wave plate that can be rotated to change polarization direction, and a transmission grating with adjustable incident angle. These dynamic adjustments enable continuous wavelength tuning across a wide range while maintaining narrow spectral width through the grating's spectral selection capability.
Solution Approach 2:
The system changes multiple parameters simultaneously: polarization state (via half-wave plate rotation), incident angle (via grating adjustment), and cavity length (via mirror positioning). These parameter changes enable wide wavelength tunability while maintaining narrow spectral width through coordinated control of all parameters.
3Power
If multiple laser diodes are stacked along fast-axis, then high power output is achieved, but wavelength tuning range is restricted
Solution Approach 1:
The transmission grating serves multiple functions: it provides optical feedback to the laser diodes, enables wavelength selection through angle adjustment, and allows polarization control in conjunction with the half-wave plate. This multi-functional design enables both high power output from multiple diodes and wide wavelength tuning through a single adjustable component.
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 achieves high power output with a tunable narrow spectral width by optimizing light feedback and beam shaping, suppressing side modes, and enabling independent wavelength adjustment of multiple modules.
Implementation Method 1
the laser beam passes through the first cylindrical lens and the second cylindrical lens in the optical system in sequence, expands in the slow axis direction to a beam with a larger cross-sectional area and a smaller divergence angle
Implementation Method 2
passes through the half wave plate to change the polarization direction, rotating the half wave plate to change the polarization direction
Implementation Method 3
passes through the transmission grating at an incident angle, adjusting the transmission grating to change the incident angle to obtain the maximum first-order diffraction efficiency
Implementation Method 4
the transmitted light is vertically incident on the output coupler mirror, and a light beam with R1 times incident power is reflected back to each laser diodes in the semiconductor laser module along the original path
Data Source
AI summary
A semiconductor laser system is used for generating wavelength tunable and narrow spectral width high power laser beam. The system includes but not limited to a semiconductor laser module and an optical system. The module consists of N laser diodes, each equipped with a fast-axis collimator, slow-axis collimator, and reflective mirror, at different height, such that on the output plane the laser beams stacked along fast-axis of the diode laser. The optical system is employed to feed a fraction of the beams with selected wavelength and spectral width back into each laser diode, which comprises a pair of cylindrical lenses, a half wave plate, a transmission grating, and an output coupler mirror.