VECSEL Modulating Mirror for Internal Laser Power Control
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Solution Overview
Problem
Conventional Vertical External Cavity Surface Emitting Lasers (VECSELs) lack a built-in modulator for controlling laser output power, necessitating external light modulators when used in display applications, such as scanning light sources for color projection in laser display apparatuses.
Innovation Solution
A VECSEL design incorporating a movable mirror unit that forms an external cavity, allowing for modulation of the laser output power without an external modulator, featuring a folding mirror, Second Harmonic Generation (SHG) crystal, and a birefringent filter to filter and convert the laser beam, enabling internal modulation of the laser beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional VECSEL configuration is used without a built-in modulator, then the device structure is simpler, but an external light modulator is required to control laser output power
Solution Approach 1:
The patent combines the modulator function with the external cavity mirror, integrating two separate components (modulator and cavity mirror) into a single unified component. This merging eliminates the need for separate external modulators while maintaining laser output control capability, directly resolving the contradiction between device simplicity and operational ease.
Solution Approach 2:
The external cavity mirror is designed to perform multiple functions simultaneously: it serves as both the cavity mirror for laser resonance and as a modulator for controlling laser output power. This multi-functionality allows the device to maintain a simple structure while enabling easy laser power control through a single component.
2Ease of operation
If an external light modulator is used to control laser output power, then laser power modulation is achieved, but the overall device complexity and size increase
Solution Approach 1:
The patent merges the modulator function with the external cavity mirror, eliminating the need for separate external modulator components. This integration reduces device complexity and size while maintaining full laser output power control capability.
Solution Approach 2:
The modulating function is extracted from a separate external modulator component and incorporated directly into the cavity mirror structure. This extraction and integration approach eliminates unnecessary external components while preserving the essential modulation capability.
3Adaptability or versatility
If a movable mirror unit is added to form an external cavity for modulation, then laser output power can be modulated internally, but the device structure becomes more complex
Solution Approach 1:
The movable mirror unit is integrated into the external cavity structure, combining the cavity formation and modulation functions into a unified design. This merging allows internal laser output modulation while minimizing structural complexity compared to adding completely separate modulation components.
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 the VECSEL to modulate laser output power internally, eliminating the need for external modulators and color wheels, allowing for full-color image projection with a compact display apparatus.
Implementation Method 1
an SHG (Second Harmonic Generation) crystal that is disposed in an optical path between the folding mirror and the movable mirror unit and converts a laser beam emitted by the laser chip into its half wavelength beam
Implementation Method 2
a birefrigent filter that is disposed in an optical path between the laser chip and the folding mirror and filters out all but a laser beam of a predetermined wavelength
Implementation Method 3
a heat sink that is attached to one surface of the laser chip and dissipates heat away from the laser chip
Data Source
AI summary
A vertical external cavity surface emitting laser (VECSEL) having an improved mirror that forms an external cavity to modulate an emitted laser beam and display apparatus employing the same are provided. The VECSEL includes: a pumping light source; a laser chip that is excited by a pump beam emitted by the pumping light source to emit a laser beam of a predetermined wavelength; a folding mirror that is separated from the laser chip and is obliquely disposed relative to an axis of incident light emitted by the laser chip and converts the propagation path of an incident laser beam; a movable mirror unit facing the folding mirror and rotates so as to selectively reflect a laser beam reflected from the folding mirror to the folding mirror. The display apparatus includes: the VECSEL having the above-mentioned structure; a light scanning unit scanning light emitted by the VECSEL to create a planar image onto the screen; and a projection optical system that is disposed between the VECSEL and the screen and enlarges and projects a laser beam onto the screen.