Diode Laser Wavelength Stabilization with Volume Bragg Grating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing diode lasers with spectrally selective feedback using volume Bragg gratings face challenges in achieving low-noise operation and a small vertical beam diameter due to manufacturing tolerances and the limitations of positioning the volume Bragg grating close to the emission surface, especially when using combined optical elements.
Innovation Solution
Dividing the vertical collimation into a volume Bragg grating with a focusing effect and a separate vertically collimating lens allows for a small distance between the volume Bragg grating and the emission surface, enabling a smaller vertical beam diameter and compensating for manufacturing tolerances by adjusting the axial position of the lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the volume Bragg grating is positioned close to the emission surface, then low-noise operation is achieved, but the vertical beam diameter increases due to the axial extension of the collimating lens
Solution Approach 1:
The patent divides the vertical collimation function into two separate optical elements: a volume Bragg grating for spectral selection and a cylindrical collimating lens for beam collimation. This segmentation allows the volume Bragg grating to be positioned close to the emission surface (within its focal length) to achieve low-noise operation, while the collimating lens is positioned separately to control the vertical beam diameter independently, thus resolving the contradiction between noise reduction and beam size control.
2Device complexity
If a single optical element combines the vertically collimating lens and volume Bragg grating, then device complexity is reduced, but manufacturing precision becomes difficult to control due to tolerances affecting the rear focal length
Solution Approach 1:
The patent separates the combined optical element into two independent components: a volume Bragg grating and a cylindrical collimating lens. This segmentation eliminates the manufacturing precision issues associated with the rear focal length of a combined element, as each component can be manufactured and adjusted independently. The volume Bragg grating handles spectral selection while the cylindrical lens handles collimation, allowing for better control over tolerances and easier adjustment to achieve the desired vertical beam diameter.
3Measurement precision
If external wavelength narrowing is achieved through surface gratings in an external cavity diode laser, then wavelength stabilization is improved, but additional optical elements are required and miniaturization becomes difficult
Solution Approach 1:
The patent merges the wavelength selection function and the collimation function into a compact arrangement where the volume Bragg grating serves as the external frequency-selective element and the cylindrical lens provides collimation. This combination achieves wavelength stabilization while minimizing the number of optical elements and enabling miniaturization, as the volume Bragg grating can be positioned very close to the diode laser emission surface, reducing the overall cavity length and device size.
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 low-noise operation with a smaller vertical beam diameter and improved beam quality by distributing refractive power across multiple optical elements, allowing for larger tolerances and better aberration suppression.
Implementation Method 1
spectrally selective feedback of the emitted radiation into the diode laser. An example of this are the so-called external cavity diode lasers (ECL), in which the feedback takes place through spectrally selective reflection at surface gratings
Implementation Method 2
Cylindrical lenses with a small focal length, so-called fast-axis collimators (FACs), are usually used to collimate the radiation in the vertical direction
Data Source
Figure 1
AI summary
The present invention relates to a low-noise, wavelength-stabilized diode laser with collimated radiation and a small beam diameter. It is an object of the present invention to provide a diode laser with wavelength stabilization and vertical collimation of the emitted radiation, which enables a small distance between the volume Bragg grating and the emission surface, a small vertical diameter of the collimated beam, and also compensation for manufacturing tolerances in the shape of the grating and the lens.According to the invention, the diode laser has an external frequency-selective element (14) for wavelength stabilization of the laser radiation, wherein the external frequency-selective element (14) has an entrance surface (16) facing the exit facet (12) and an exit surface (18) facing away from the exit facet (12) and is formed by a volume Bragg grating; and wherein the external frequency-selective element (14) is configured such that the divergence of the radiation exiting the exit facet (12) is reduced when passing through the external frequency-selective element (14). This can be achieved, for example, by a curved exit surface (18).