VeCSEL Dual-Frequency THz Generation via Mode Shaping
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Solution Overview
Problem
Current terahertz laser sources face challenges in achieving compact, stable, continuously tunable, coherent, and powerful dual-frequency operation, with existing solutions often being cumbersome, limited in output power, coherence, or requiring complex setups and low temperatures.
Innovation Solution
A vertical external cavity surface emitting laser (VeCSEL) device with a mask having non-uniform absorbance and photonic crystals or diffraction gratings to select and stabilize transverse modes, allowing for high coherence and tunability over a wide frequency range while operating at room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two distinct laser sources are used for THz generation, then frequency tunability is improved, but frequency stability deteriorates due to drift effects
Solution Approach 1:
The patent merges two laser sources into a single laser source that generates two transverse modes. This is achieved by using a single laser cavity with specific geometric parameters (cavity length L, mirror curvature radius R) that support multiple transverse modes, thereby combining the functions of two separate sources while maintaining frequency stability through common-mode sensitivity to environmental changes.
Solution Approach 2:
The patent segments the laser output into two distinct transverse modes (TEM00 and TEM01) with different frequencies. This is accomplished by designing the laser cavity with specific dimensions that allow simultaneous oscillation of multiple transverse modes, each with its own frequency, while maintaining stability through the common cavity structure.
2Adaptability or versatility
If two laser sources are used for THz generation, then frequency tunability is improved, but device complexity increases
Solution Approach 1:
The patent combines two laser sources into one integrated laser device that generates two transverse modes. This reduces system complexity by eliminating the need for two separate laser sources, their respective control systems, and alignment mechanisms, while still providing dual-frequency output for THz generation.
3Reliability
If spectral filters are used in external cavity laser, then frequency stability is improved, but output power decreases
Solution Approach 1:
The patent incorporates frequency selection directly into the laser cavity design through specific geometric parameters (cavity length L, mirror curvature radius R) that naturally support multiple transverse modes with stable frequencies. This preliminary configuration eliminates the need for additional spectral filters that would attenuate the beam and reduce output power.
4Adaptability or versatility
If intracavity moving elements are used for mode separation, then frequency tunability is improved, but device complexity and robustness deteriorate
Solution Approach 1:
Instead of using moving elements to achieve frequency tuning, the patent inverts the approach by designing a fixed cavity with specific geometric parameters that naturally support multiple transverse modes. The frequency selection is achieved through the cavity geometry itself rather than through mechanical adjustment, thereby improving robustness while maintaining tunability through thermal or electrical control of the active medium.
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 solution enables stable, robust, and highly coherent dual-frequency operation with fine tunability, achieving high output power and stability without complex alignments or mechanical noise, suitable for terahertz generation.
Implementation Method 1
at least one mask, each mask being arranged with a surface having a non-uniform absorbance
Implementation Method 2
comprise at least one photonic crystal and/or a diffraction grating located at at least one end of the gain region and arranged to shape the transverse phase and/or the transverse intensity of the optical wave
Implementation Method 3
comprise at least one photonic crystal and/or a diffraction grating located at at least one end of the gain region and arranged to shape the transverse phase and/or the transverse intensity of the optical wave
Data Source
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AI summary
The invention relates to a laser device (100) for generating an optical wave (107) including at least two frequencies, wherein one such laser device (100) includes: a first element (111) including a gain region (104), a second mirror (106) that is separate from the first element (111) and is arranged so as to form, together with the first mirror (103), an optical cavity including the gain region (104), and means (120) for pumping the gain region (104) so as to generate the optical wave (107). Said laser device (100) further includes: means for shaping the light intensity of the optical wave (107), which means are arranged to select at least two transverse modes of the optical wave (107); and means for shaping the longitudinal and/or transverse phase profile of the optical wave (107), which means are arranged to adjust the at least two transverse modes of the optical wave (107).