A wavelength tunable fabry-perot micro-laser

Abstract

The application belongs to the field of laser technology, and particularly relates to a wavelength tunable Fabry-Perot micro laser. The micro laser realizes wideband tuning of laser output wavelength by introducing a convex-shaped dielectric micro structure into a wedge-shaped Fabry-Perot micro cavity. The wedge-shaped Fabry-Perot micro cavity is composed of two non-parallel cavity mirrors. The convex-shaped dielectric micro structure is made on the surface of one of the cavity mirrors and is composed of a rectangular waveguide and a rectangular micro structure with a size larger than the rectangular waveguide. Based on the micro cavity structure, continuous wideband tuning of the laser output wavelength can be realized by moving the excitation position of the pumping light along the direction of the rectangular waveguide or adjusting the tilt angle of the cavity mirror under the condition that the pumping position is fixed at the end of the waveguide. The application realizes wideband tuning without the need of preparing multiple different gain materials or multiple cavity structures, has a simple structure and high integration, and provides a new technical approach for the realization of a wideband tunable laser on a chip.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more particularly to a wavelength-tunable Fabry-Perot microlaser. Background Technology

[0002] Micro- and nano-lasers have become the core light source for on-chip photonic systems due to their advantages such as large-scale integration compatibility, small mode size, and high coherence emission. Among these advantages, the broadband tunability of laser emission is crucial for chip-level photonic devices, such as full-color laser displays, wavelength division multiplexing (WDM) light sources, and encryption chips. Specifically, in next-generation laser displays, fine tuning of the laser wavelength over a wide range can significantly expand the color gamut. In WDM communication systems, monolithically integrated multi-wavelength laser arrays act as the basic transmitter, where the number of laser wavelength channels directly determines the transmission capacity. Furthermore, in micro- and nano-laser-based encryption chips, wavelength manipulation provides an effective mechanism for encoding optical information. Therefore, the achievable tuning bandwidth plays a key role in both encryption capacity and security. Thus, the development of micro- and nano-lasers with broadband wavelength tunability is increasingly important for advanced photonic integrated systems.

[0003] Currently, wavelength tuning of micro / nano lasers is mainly achieved through two mechanisms: optical gain modulation or cavity loss modulation. For gain modulation, the most typical approach is to use gain materials with different emission spectra to cover the target wavelength band. For example, three droplet microcavities with red, green, and blue emission bands respectively can form an RGB laser display pixel, and wavelength tuning can then be achieved by selectively pumping the target cavity. To improve tuning accuracy, the Förster resonant energy transfer laser mechanism is employed, which involves mixing two gain materials within a single cavity. However, since the laser wavelength is largely determined by the composition of the gain material, achieving continuous wavelength tuning remains challenging. Regarding cavity loss modulation, the laser wavelength is controlled by modulating the oscillation threshold spectrum. Under a fixed cavity loss, the longitudinal mode with the lowest threshold is preferentially selected to oscillate, determining the center laser wavelength. Therefore, broadband tuning can be achieved by integrating microcavities with different losses, with the tuning bandwidth depending on the range of loss differences between the microcavities. Accordingly, continuous wavelength tuning typically requires the fabrication of a series of microcavities with gradually varying losses. However, this method not only increases the complexity of fabrication and reduces the overall integration, but also most of the microcavities adopt a whispering-gallery mode configuration, which has problems such as poor directionality and low energy extraction efficiency.

[0004] Therefore, achieving wavelength tuning of micro / nano lasers that simultaneously possess broadband, high integration, and high output directionality is a major challenge.

[0005] To address the aforementioned issues, this invention proposes a wavelength-tunable Fabry-Perot microlaser based on a novel cavity structure design. This design achieves broadband tuning of the laser output wavelength by introducing a specific "convex"-shaped dielectric microstructure within a wedge-shaped Fabry-Perot microcavity. The "convex"-shaped dielectric microstructure is fabricated on the surface of a cavity mirror and consists of a rectangular waveguide and a rectangular microstructure larger than the waveguide. Based on this microcavity structure, continuous broadband tuning of the laser output wavelength can be achieved by precisely controlling the excitation position of the pump light on the waveguide or actively adjusting the tilt angle between the cavity mirrors. This invention achieves broadband tuning without requiring the fabrication of multiple different gain materials or multi-cavity structures, exhibiting a simple structure and high integration, providing a new technical approach for realizing on-chip broadband tunable lasers. Summary of the Invention

[0006] The purpose of this invention is to propose a wavelength-tunable Fabry-Perot microlaser, aiming to solve the technical challenge of achieving broadband continuous tuning, high integration, and high directional output in a single microlaser in existing technologies. To achieve this objective, the invention integrates a convex dielectric microstructure on the surface of one cavity mirror within a wedge-shaped Fabry-Perot microcavity, thereby achieving broadband continuous tuning, high integration, and high directional output. The wedge-shaped Fabry-Perot microcavity consists of two non-parallel cavity mirrors, and the convex structure comprises a rectangular waveguide and a larger rectangular microstructure. Based on this design, precise and continuous dynamic tuning of the laser wavelength can be achieved by moving the excitation position of the pump light along the rectangular waveguide direction, or by adjusting the tilt angle of the cavity mirror at a fixed pump position.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A wavelength-tunable Fabry-Perot microlaser is characterized by comprising a wedge-shaped Fabry-Perot microcavity consisting of a first cavity mirror and a second cavity mirror, a dielectric microstructure fabricated on the surface of the first cavity mirror and located between the first cavity mirror and the second cavity mirror, and a gain medium filling the space defined by the first cavity mirror and the second cavity mirror and covering the dielectric microstructure. The dielectric microstructure includes a first region and a second region connected sequentially along a first direction. The first region and the second region are rectangular structures in the plane of the first cavity mirror. The width of the second region is greater than the width of the first region, so that the dielectric microstructure as a whole is convex in the plane of the first cavity mirror.

[0008] Furthermore, the first direction is consistent with the wedge direction formed between the first cavity mirror and the second cavity mirror. By changing the excitation position of the pump light in the first region, or by changing the tilt direction of the second cavity mirror relative to the first cavity mirror, the output wavelength of the microlaser can be continuously adjusted.

[0009] Furthermore, the gain medium is a fluorescent dye solution.

[0010] Furthermore, the length of the first region is 50-100 micrometers and the width is 10-25 micrometers; the length of the second region is not less than 100 micrometers and its width is greater than the width of the first region.

[0011] Furthermore, the tilt angle of the second cavity mirror is adjustable, and its adjustment range is such that the angle between the first cavity mirror and the second cavity mirror is 0.01° to 0.05°.

[0012] Second, the present invention provides a wavelength tuning method based on the above-mentioned wavelength-tunable Fabry-Perot microlaser, characterized by comprising the following steps: Adjust the tilt angle of the second cavity mirror so that the wedge-shaped direction points from the first region to the second region; The pump light excitation position is set on the first region; The excitation position of the pump light is moved along the first direction to achieve continuous tuning of the laser output wavelength towards the longer wavelength direction.

[0013] Third, the present invention provides a wavelength tuning method based on the above-mentioned wavelength-tunable Fabry-Perot microlaser, characterized by comprising the following steps: The excitation position of the pump light is fixed at one end of the first region; Adjusting the tilt angle of the second cavity mirror allows the wedge direction to switch between pointing from the first region to the second region and pointing from the second region to the first region, thereby achieving tuning of the laser output wavelength.

[0014] Compared with existing technologies, the advantages of this invention are as follows: This invention abandons the traditional tuning approach that relies on multi-material gain media or multi-cavity loss arrays. Through a single, integrated cavity structure and simple adjustment of the pump position or cavity mirror tilt angle, broadband and continuous wavelength tuning can be achieved. This significantly simplifies the device structure and fabrication process, improves system integration and reliability, while maintaining the inherent high directivity output characteristics of the Fabry-Perot cavity, effectively overcoming the inherent defect of poor directivity in whispering-gallery mode microcavities. This wavelength-tunable microlaser can be applied to high-capacity on-chip wavelength division multiplexing communication light sources, full-color integrated laser displays, high-security optical encryption chips, and optical sensing, providing a core light source solution for the development of high-performance, highly integrated on-chip photonic information systems. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the wavelength-tunable Fabry-Perot microlaser structure according to an embodiment of the present invention.

[0016] Among them: 1. First cavity mirror; 2. Second cavity mirror; 3. Dielectric microstructure; 4. Gain medium; 5. Pump light.

[0017] Figure 2 This is a schematic diagram of a laser wavelength tuning method according to an embodiment of the present invention. a is a schematic diagram of wavelength tuning achieved by changing the excitation position of the pump light on the rectangular waveguide in the first region; b is a laser spectrum diagram of different positions of the rectangular waveguide in the first region pumped along the first direction (X direction).

[0018] Among them: 6. Scan the laser emission spectrum corresponding to the pump light excitation position along the extension direction of the rectangular waveguide in the first region. The broken line in the figure connects the average wavelength of the spectrum at each pump position, showing the trend of wavelength change with pump position.

[0019] Figure 3 This is a schematic diagram of a second laser wavelength tuning method according to an embodiment of the present invention. a) is a schematic diagram showing the adjustment of the tilt direction of the second cavity mirror from the first region to the second region, wherein the pump position is at the endpoint of the rectangular waveguide in the first region; b) is a laser spectrum emitted from the microcavity shown in a; c) is a schematic diagram showing the adjustment of the tilt direction of the second cavity mirror from the second region to the first region, wherein the pump position is at the endpoint of the rectangular waveguide in the first region; d) is a laser spectrum emitted from the microcavity shown in c.

[0020] Wherein: 7. Laser output spectrum when pointing from the first region rectangular waveguide to the larger second region rectangular microstructure in the non-parallel angle direction of the cavity mirror; 8. Laser output spectrum when pointing from the larger second region rectangular microstructure to the first region rectangular waveguide in the non-parallel angle direction of the cavity mirror. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described below.

[0022] This invention proposes a wavelength-tunable Fabry-Perot microlaser, integrating a convex dielectric microstructure into a wedge-shaped Fabry-Perot (FP) microcavity. By precisely controlling the excitation position of the pump light on the waveguide or actively adjusting the tilt angle between the cavity mirrors, continuous and broadband tuning of the laser output wavelength is achieved. The technical solution of this invention will be systematically and thoroughly described below with reference to the accompanying drawings and specific implementation details.

[0023] The overall structure of the wavelength-tunable FP microlaser in this embodiment is as follows: Figure 1 As shown. It includes: a first cavity mirror 1, a second cavity mirror 2, a "convex" shaped dielectric microstructure 3, a fluorescent dye solution 4, and a pump light 5 for excitation.

[0024] Both the first cavity mirror 1 and the second cavity mirror 2 have a high-reflectivity film coated on their respective inner surfaces. The high-reflectivity band is 570-700 nm, and the reflectivity is 99.5%. The non-parallel angle between the first cavity mirror 1 and the second cavity mirror 2 can be adjusted by adjusting the mounting bracket of the second cavity mirror 2.

[0025] The dielectric microstructure 3 is fabricated on the inner surface of the first cavity mirror 1, such as... Figure 1 As shown, the structure extends along a specific direction (defined as the X direction, i.e., the first direction) and comprises two regions with different widths (dimensions perpendicular to the X direction). The region closer to one end is the first region, with a narrower width W1 (10-25 micrometers) and a length L1 of 50-100 micrometers. Adjacent to the first region is the second region, with a width W2 greater than W1 (e.g., W2 ≥ 2 × W1) and a length L2 ≥ 100 micrometers. A step-like abrupt change in width occurs at the junction of the first and second regions. The entire structure is convex in shape within the mirror plane of the first cavity mirror 1.

[0026] Gain medium 4 is encapsulated between the first cavity mirror 1 and the second cavity mirror 2, and is completely immersed in the stepped dielectric microstructure 3. Gain medium 4 is a fluorescent dye solution dissolved in a mixed solvent. In this embodiment, a 15 mM Rhodamine 6G dye is used, wherein the solvent contains 98% deionized water and 2% alcohol, which can absorb pump light in the green light band and provide optical gain in the yellow-orange to red light band.

[0027] Based on the above structure, the present invention provides two methods for laser wavelength tuning: The first method is achieved by scanning the pump light excitation position along the extension direction of the rectangular waveguide in the first region, such as... Figure 2 As shown, the specific steps include the following: 1. Adjust the tilt angle of the second cavity mirror 2 so that the direction of the non-parallel angle formed between the second cavity mirror 2 and the first cavity mirror 1 is from the rectangular waveguide to the larger rectangular microstructure, and the non-parallel angle is about 0.02°; The pump light 5 is a 532 nm nanosecond pulsed laser that is incident perpendicularly from one side of the second cavity mirror 2. After being focused, it can act on one end of the first region rectangular waveguide in the stepped dielectric microstructure 3, and move the excitation position of the pump light 5 along the extension direction of the first region rectangular waveguide, thereby realizing the laser wavelength shifting to the longer wavelength direction.

[0028] like Figure 2As shown, as the pump position moves, the laser output wavelength undergoes a continuous redshift (shifting towards longer wavelengths). The principle behind the first method of wavelength tuning is as follows: the first region primarily confines and guides the optical field, forming a FP resonant channel; the second region, due to its larger size, causes some loss to the optical field guided from the first region. Because the degree of loss in the second region on the oscillating optical field in the first region varies at different pump positions, the oscillating optical field has different wavelengths.

[0029] The second method is achieved by changing the tilt direction of the second cavity mirror 2, such as... Figure 3 As shown. Specifically, it includes the following steps: 1. Adjust the tilt angle of the second cavity mirror 2 so that the non-parallel angle formed between the second cavity mirror 2 and the first cavity mirror 1 points from the first region rectangular waveguide to the larger second region rectangular microstructure.

[0030] 2. The excitation position of the pump light 5 is set at one end of the rectangular waveguide in the first region of the "convex" shaped dielectric microstructure 3; 3. Adjust the tilt angle of the second cavity mirror 2 again, changing the wedge direction from pointing from the first region to the second region to pointing from the second region to the first region, thus reversing the wedge direction. In this case, the second region will no longer cause loss to the oscillating optical field in the rectangular waveguide of the first region, allowing the laser wavelength to switch to a longer wavelength, thereby achieving wavelength transition or wide-range tuning. By controlling the size of the wedge angle, continuous transition tuning between the two states can also be achieved.

[0031] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A wavelength-tunable Fabry-Perot microlaser, characterized in that, It includes a wedge-shaped Fabry-Perot microcavity consisting of a first cavity mirror (1) and a second cavity mirror (2), a dielectric microstructure (3) fabricated on the surface of the first cavity mirror (1) and located between the first cavity mirror (1) and the second cavity mirror (2), and a gain medium (4) filling the space defined by the first cavity mirror (1) and the second cavity mirror (2) and covering the dielectric microstructure (3). The dielectric microstructure (3) includes a first region and a second region connected sequentially along a first direction. The first region and the second region are rectangular structures in the mirror plane of the first cavity mirror (1). The width of the second region is greater than the width of the first region, so that the dielectric microstructure (3) as a whole is convex in the mirror plane of the first cavity mirror (1).

2. The wavelength-tunable Fabry-Perot microlaser according to claim 1, characterized in that, The first direction is consistent with the wedge direction formed between the first cavity mirror (1) and the second cavity mirror (2). By changing the excitation position of the pump light (5) in the first region, or by changing the tilt direction of the second cavity mirror (2) relative to the first cavity mirror (1), the output wavelength of the microlaser can be continuously adjusted.

3. The wavelength-tunable Fabry-Perot microlaser according to claim 1, characterized in that, The gain medium (4) is a fluorescent dye solution.

4. The wavelength-tunable Fabry-Perot microlaser according to claim 1, characterized in that, The first region has a length of 50-100 micrometers and a width of 10-25 micrometers; the second region has a length of not less than 100 micrometers and a width greater than that of the first region.

5. The wavelength-tunable Fabry-Perot microlaser according to claim 1, characterized in that, The tilt angle of the second cavity mirror (2) is adjustable, and its adjustment range is such that the angle between the first cavity mirror (1) and the second cavity mirror (2) is 0.01° to 0.05°.

6. A wavelength tuning method for a Fabry-Perot microlaser based on any one of claims 1-5, characterized in that, Includes the following steps: Adjust the tilt angle of the second cavity mirror (2) so that the wedge direction points from the first region to the second region; The excitation position of the pump light (5) is set on the first region; The excitation position of the pump light (5) is moved along the first direction to achieve continuous tuning of the laser output wavelength towards the long wavelength direction.

7. A wavelength tuning method for a Fabry-Perot microlaser based on any one of claims 1-5, characterized in that, Includes the following steps: The excitation position of the pump light (5) is fixed at one end of the first region; Adjust the tilt angle of the second cavity mirror (2) so that the wedge direction switches between pointing from the first region to the second region and pointing from the second region to the first region, so as to achieve the tuning of the laser output wavelength.

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