Tunable External Resonator Laser Dispersion Compensation
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Solution Overview
Problem
Littman-type tunable external resonator lasers face challenges in achieving mode-hop-free tuning due to large refractive index dispersion, particularly at short wavelengths, limiting their tuning range and power output, especially when using long laser diode chips which increase chromatic dispersion.
Innovation Solution
A tunable external resonator laser design that corrects group velocity dispersion by adjusting the parallel movement of the diffraction grating and mirror, using a formula to calculate offset values for the grating and mirror positions, ensuring mode-hop-free tuning across a broader wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a long laser diode chip is used to increase power output, then power output is improved, but chromatic dispersion increases causing mode-hop
Solution Approach 1:
The patent applies parameter changes by introducing a dispersion compensation grating with specific groove density and orientation angle. By changing the physical parameters of the grating (groove density, angle relative to optical axis), the system compensates for chromatic dispersion introduced by the long laser diode chip, enabling mode-hop-free tuning across broader wavelength ranges while maintaining high power output capability
Solution Approach 2:
The dispersion compensation grating serves as an intermediary element between the laser diode chip and the main diffraction grating. This intermediate component specifically addresses the chromatic dispersion problem by introducing opposite dispersion characteristics, allowing the system to simultaneously achieve high power output (via long chip) and mode-hop-free operation
2Adaptability or versatility
If tuning range is extended to short wavelengths, then broadband tuning is improved, but refractive index dispersion increases causing mode-hop
Solution Approach 1:
The patent uses parameter changes by configuring the dispersion compensation grating with specific orientation angles and groove densities that are optimized for short wavelength operation. The grating's geometric parameters are carefully selected to counteract the increased refractive index dispersion that occurs at short wavelengths, enabling reliable mode-hop-free tuning across an extended broadband range including short wavelengths
3Reliability
If parallel movement of diffraction grating and mirror is adjusted to correct dispersion, then mode-hop-free tuning is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by making the dispersion compensation grating a fixed component with predetermined geometric characteristics (specific groove density and orientation angle). Rather than requiring active adjustment mechanisms for all components, only local parameter optimization of the grating itself is needed, thereby achieving mode-hop-free tuning without significantly increasing overall device complexity
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
Enables mode-hop-free tuning over a wider range, even at short wavelengths, and supports high power output and broadband tuning capabilities, overcoming the limitations of existing designs.
Implementation Method 1
a diffraction grating which diffracts the light collimated by the lens
Implementation Method 2
a movable mirror which reflects the light diffracted by the diffraction grating
Implementation Method 3
a lens which collimates the light emitted from the laser chip
Data Source
Figure 1~2
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Figure 5~6
AI summary
To provide a tunable external resonator laser with mode-hop-free for broadband. For solving the problem, in a tunable external laser comprising, the offset is given between the pivot and the diffraction grating. The tunable external resonator laser comprising, a laser chip which emits light; a lens which collimates the light emitted from said laser chip, a diffraction grating which diffracts the light collimated by said lens, a support body which said diffraction grating is fixed, and a movable mirror which reflects the light diffracted by said diffraction grating, wherein said diffraction grating is arranged apart a prescribed distance from a Littman-type tunable external resonator laser arrangement in which said movable mirror rotates on a pivot which is the intersection point of the surface of said movable mirror and the surface of the said diffraction grating.