A system for all-optical continuous wavelength tuning based on whispering gallery microcavity lasers

Abstract

The present invention discloses a system based on a whispering gallery microcavity laser that can realize all-optical continuous wavelength tuning, including: a microcavity laser realization device and an adjustment module; the microcavity laser realization device is used to emit pump light to a whispering gallery microcavity and generate a whispering gallery microcavity laser; the adjustment module is used to continuously and finely adjust the output wavelength of the pump light, thereby realizing all-optical continuous wavelength tuning of the whispering gallery microcavity laser. The all-optical wavelength continuous tuning realization method proposed in the present invention is simple to operate, and only requires changing the wavelength of the pump laser light source, and using the photothermal effect to continuously tune the wavelength of the output microcavity laser. Compared with other methods based on photothermal materials, mechanical tuning, etc., the all-optical tuning technical means proposed in the present invention has the advantages of simple realization device and easy operation. In addition, the all-optical tuning technology based on the whispering gallery microcavity laser uses the dense mode in the whispering gallery microcavity as a premise to excite the laser mode, and has the advantages of low laser threshold, small size, and low production cost.

Description

Technical Field

[0001] The invention relates to the field of laser technology, and in particular to a system capable of realizing continuous all-optical wavelength tuning based on a whispering gallery microcavity laser. Background Art

[0002] All-optical wavelength-tunable micro-lasers are one of the frontier directions of basic research and technological applications today. Due to the ultra-high quality factor and small mode volume of the whispering gallery microcavity, the microcavity laser based on the whispering gallery mode has excellent characteristics such as narrow linewidth and low threshold power. In recent years, it has been widely used in nonlinear optics, laser sensing, cavity optomechanics and other fields. Among them, the luminescence based on rare earth elements can cover the region from ultraviolet to near-infrared, and has broad prospects in laser applications. The energy density in the whispering gallery microcavity is extremely high, and the interaction between light and matter is greatly enhanced. Therefore, in practical applications, whispering gallery microcavity lasers are widely used. At present, the common methods of tuning the whispering gallery microcavity are generally external tuning methods such as mechanical tuning and electro-optical tuning. Although this external regulation has a large tuning range, its tuning accuracy depends on the size of the microcavity and the stability of the external tuning means, and the required system is relatively complex. For example, the mechanical tuning method generally requires the microcavity to be stretched or compressed by external force, and the resonant frequency of the microcavity is tuned by changing its size. The operation is complicated and the tuning accuracy is poor. All-optical tuning is easy to operate, has good stability, and can tune the laser wavelength over a wide range, making it an effective way to achieve continuous wavelength tuning of whispering gallery microcavity lasers. Summary of the invention

[0003] In order to solve the problems of complex tuning structure and low tuning accuracy of existing microcavity lasers, the present invention provides a system based on whispering gallery microcavity lasers that can achieve all-optical wavelength continuous tuning. First, the silica whispering gallery microcavity generates microcavity lasers through the micro-nano fiber-microcavity coupling method, and then the output wavelength of the pump light is continuously tuned through the adjustment module, and the photothermal effect of the silica material itself is used to achieve all-optical wavelength continuous tuning of the output microcavity laser.

[0004] To achieve the above-mentioned purpose, the present invention provides a system based on a whispering gallery microcavity laser that can realize all-optical wavelength continuous tuning, comprising: a microcavity laser realization device and an adjustment module;

[0005] The microcavity laser realization device is used to emit pump light to the whispering gallery microcavity and generate whispering gallery microcavity laser;

[0006] The adjustment module is used to continuously and finely adjust the output wavelength of the pump light, thereby realizing continuous tuning of the all-optical wavelength of the whispering gallery microcavity laser.

[0007] Preferably, the microcavity laser realization device comprises: a pump source, an isolator, a polarization controller, a silica microcavity, a micro-nano optical fiber, a coupler, a photodetector, an oscilloscope, and a spectrometer which are connected in sequence to form an optical fiber loop.

[0008] Preferably, the micro-nano optical fiber and the silica microcavity are placed vertically in space to achieve light field coupling to excite the whispering gallery mode on the surface of the microcavity, thereby generating microcavity laser. The micro-nano optical fiber is formed by taper of single-mode optical fiber, with a diameter of 1-3 μm; the silica microcavity includes: passive silica microcavity and rare earth element doped silica microcavity; the microcavity shape includes spherical, bottle-shaped and ring-shaped, the size includes 100-500 μm, and the quality factor is ≥10 7 .

[0009] Preferably, in the microcavity structure, pump light enters the silica microcavity through micro-nano optical fiber coupling, produces light amplification through the nonlinear effect of the light field or the stimulated radiation of rare earth ions, and finally produces the whispering gallery microcavity laser after multiple energy accumulation and mode selection in the whispering gallery microcavity.

[0010] Preferably, the working process of the adjustment module includes: the adjustment module outputs a triangular wave signal to control the pump source, so that the laser output wavelength of the pump source continuously changes with a wavelength accuracy of the order of picometers, so that the output wavelength of the whispering gallery microcavity laser generated by the pump source also continuously redshifts, thereby realizing continuous tuning of the all-optical wavelength of the whispering gallery microcavity laser.

[0011] Preferably, the working principle of the all-optical wavelength continuous tuning includes: based on the premise that the pump light is coupled into the silica microcavity to generate the whispering gallery microcavity laser, when the pump laser coupled into the microcavity gradually accumulates, the temperature in the microcavity can be increased due to the photothermal effect of the silica material. At this time, the refractive index of the material and the size of the microcavity change, thereby causing the wavelength of the whispering gallery microcavity laser to redshift, and the relationship between the wavelength redshift and the temperature satisfies:

[0012]

[0013] Among them, λ 0 is the initial microcavity laser wavelength; is the coefficient of thermal expansion; is the thermo-optical coefficient; r represents the output wavelength of the final microcavity laser; ΔT represents the temperature change.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The all-optical wavelength continuous tuning method proposed in the present invention is simple to operate. It only requires changing the wavelength of the pump laser light source and using the photothermal effect to continuously tune the wavelength of the output microcavity laser. Compared with other methods based on photothermal materials and mechanical tuning, the all-optical tuning technology proposed in the present invention has the advantages of simple device, easy operation, and high tuning accuracy.

[0016] (2) In addition, the all-optical wavelength continuous tuning system proposed in the present invention is based on the premise of utilizing the dense modes in the whispering gallery microcavity to excite the laser mode. The laser produced has the advantages of small size, low production cost, low laser threshold, good stability, etc., and has great potential and value in future optical communications, lidar and optical sensing applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 A schematic diagram of the system structure provided by an embodiment of the present invention;

[0019] Figure 2 A schematic structural diagram of a micro-nano optical fiber taper and a bottle-shaped microcavity coupled system doped with rare earth erbium ions provided in an embodiment of the present invention;

[0020] Figure 3 A measured transmission spectrum of the quality factor of a bottle-shaped microcavity doped with rare earth erbium ions at 1550nm provided in an embodiment of the present invention;

[0021] Figure 4 The transmission power curve of the whispering gallery mode excited by the bottle-shaped microcavity doped with rare earth erbium ions and the time variation curve of the microcavity laser mode provided by the embodiment of the present invention;

[0022] Figure 5 A spectrum diagram based on wavelength tuning of a whispering gallery microcavity laser provided in an embodiment of the present invention;

[0023] Figure 6 A fitting curve diagram of the pump wavelength and output laser wavelength of a whispering gallery microcavity laser is provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 As shown, it is a schematic diagram of the system structure of an embodiment of the present invention, including: a microcavity laser implementation device and an adjustment module 10; the microcavity laser implementation device is used to emit pump light to the whispering gallery microcavity structure and generate a whispering gallery microcavity laser; the adjustment module 10 is used to continuously and finely adjust the output wavelength of the pump light, thereby realizing continuous tuning of the all-optical wavelength of the whispering gallery microcavity laser.

[0027] The following will describe in detail how the present invention solves technical problems in real life in conjunction with the present embodiment.

[0028] First, the pump source 1 emits pump light, which is input into the microcavity structure to generate whispering gallery microcavity laser; in this embodiment, the pump source is a tunable laser with an operating band of 1450nm. In this embodiment, the microcavity laser realization device includes, in addition to the pump source 1, an isolator 2, a polarization controller 3, a silica microcavity doped with rare earth erbium ions 4, a micro-nano optical fiber 5, a coupler 6, a photodetector 7, an oscilloscope 9, and a spectrometer 8, which are connected in sequence to form an optical fiber loop, such as Figure 1 As shown. Among them, the isolator 2 is used to prevent the reflected microcavity laser from returning to the pump source laser, which plays a role in protecting the pump source laser; the polarization controller 3 is used to adjust the polarization state of the input light coupled into the microcavity; the output end of the coupler 6 is divided into two paths, one of which is connected to the photodetector 7 and the oscilloscope 9 in turn to record the whispering gallery mode excited on the microcavity surface; the other is connected to the spectrometer 8 to record the spectral information of the generated microcavity laser. The shapes of the microcavity include spherical, bottle-shaped, ring-shaped, etc., the sizes include 100-500μm, and the quality factor ≥10 7 .

[0029] The whispering gallery microcavity laser of this embodiment uses the method of micro-nano fiber-microcavity coupling to input pump light into the silica whispering gallery microcavity doped with rare earth elements to generate microcavity laser. Specifically, the silica microcavity 4 doped with rare earth ions (erbium ions in this embodiment) and the micro-nano fiber 5 constitute a microcavity coupling system, such as Figure 2As shown. The micro-nano optical fiber 5 is a commercial single-mode optical fiber that is tapered, and the diameter of the cone region is 1-3μm (the value in this embodiment is 2μm). The two are placed vertically in space to couple, and the relative distance of the coupling can be precisely adjusted to excite different whispering gallery modes on the surface of the microcavity. Specifically, the pump light is coupled into a rare earth element-doped (erbium ions are selected in this embodiment) silica microcavity (a bottle-shaped microcavity is selected in this embodiment) through the micro-nano optical fiber. After the rare earth ions absorb the energy of the pump light, they are stimulated to transition to a high energy level, forming a population inversion, and then stimulated radiation to produce light amplification. In addition to the use of rare earth element-doped silica whispering gallery microcavity, undoped passive silica microcavity can also be used. The pump light is coupled into the passive silica microcavity through the micro-nano optical fiber. Light amplification can also be produced through the nonlinear effects of the light field (such as Raman scattering, Brillouin scattering). After multiple energy accumulations and mode selections in the whispering gallery microcavity, the whispering gallery microcavity laser is finally produced.

[0030] In this embodiment, the silica microcavity 4 doped with rare earth erbium ions can be formed by dipping the end of the silica optical fiber into an acetone solution containing erbium ions for many times and heating and melting the end of the optical fiber with a carbon dioxide laser. In addition, the microcavity in this embodiment is a bottle-shaped microcavity with a maximum diameter of 200 μm, and its quality factor measurement transmission spectrum is as follows: Figure 3 As shown, the quality factor of the microcavity can reach 4.5×10 7 .

[0031] Finally, the adjustment module 10 is used to adjust the output wavelength of the pump light, thereby realizing the all-optical continuous wavelength tuning of the whispering gallery microcavity laser. The specific working process is as follows: the adjustment module outputs a triangular wave signal to control the pump source, so that the laser output wavelength of the pump source changes continuously with a wavelength accuracy of the order of picometers. Due to the photothermal effect of the silica material, the temperature in the microcavity can be increased, thereby causing the excited whispering gallery microcavity mode to undergo triangular wave broadening, that is, the resonance mode redshifts over time, such as Figure 4 As shown by the solid curve. When the pump power is further increased, as the energy accumulates, the whispering gallery microcavity laser is generated, and its output wavelength also undergoes a continuous red shift, as shown in Figure 4 As shown in the scattered curve of , the all-optical continuous wavelength tuning of the whispering gallery microcavity laser is realized.

[0032] The working principle of the above all-optical wavelength continuous tuning is mainly based on the photothermal effect of silica materials. Specifically, when the pump light is coupled into the whispering gallery microcavity to generate microcavity laser, when the pump laser coupled into the microcavity gradually accumulates, the temperature in the microcavity will increase due to the photothermal effect of silica materials. At this time, the refractive index of the material and the size of the microcavity will change, which will cause the wavelength of the whispering gallery microcavity laser to redshift. The relationship between the wavelength redshift and temperature satisfies:

[0033]

[0034] Among them, λ 0 is the initial microcavity laser wavelength; is the coefficient of thermal expansion; is the thermo-optical coefficient; r represents the output wavelength of the final microcavity laser; ΔT represents the temperature change.

[0035] like Figure 5 As shown in the figure, it is a spectrum diagram of wavelength tuning of the whispering gallery erbium-doped bottle-shaped microcavity laser. It can be seen that when the pump laser wavelength is continuously changed at a wavelength step of 20pm (i.e., continuously adjusted from 1460.07nm to 1460.24nm), the output microcavity laser wavelength will also undergo a continuous red shift (i.e., continuously change from 1553.307nm to 1553.48nm), thereby realizing the continuous tuning of the all-optical wavelength of the whispering gallery microcavity laser. And as the light coupled into the cavity increases, the intensity of the output laser also increases.

[0036] like Figure 6 The figure shows the fitting curve of the pump wavelength and the output laser wavelength of the whispering gallery erbium-doped bottle microcavity laser. It can be seen that the change of the pump laser wavelength has a good linear relationship with the drift of the output laser wavelength. The maximum tunable range is 0.181nm (corresponding to 24.8GHz), and the linearity is as high as 99.95%.

[0037] It can be seen from the above embodiments that based on the microcavity laser provided by the present invention, the laser produced has the advantages of small size, low production cost, low laser threshold, good stability, etc., based on the premise of utilizing the dense modes in the whispering gallery microcavity to excite the laser mode. The invention utilizes the photothermal effect of the silica microcavity, and the all-optical tuning of the output microcavity laser can be tuned only by changing the resonance wavelength of the whispering gallery microcavity. Compared with other methods based on photothermal materials, mechanical tuning, etc., the all-optical tuning technology proposed in the present invention has the advantages of simple device implementation, easy operation, high tuning accuracy, etc., and has great potential and value in future optical communications, lidar, and optical sensing applications.

[0038] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A system based on whispering gallery microcavity lasers that can achieve all-optical wavelength continuous tuning, characterized in that: include: Microcavity laser realization device and adjustment module; The microcavity laser realization device is used to emit pump light to the whispering gallery microcavity and generate whispering gallery microcavity laser; The microcavity laser realization device comprises: a pump source, an isolator, a polarization controller, a silica microcavity, a micro-nano optical fiber, a coupler, a photodetector, an oscilloscope, and a spectrometer; wherein the pump source, the isolator, and the polarization controller are sequentially connected in a forward direction; the silica microcavity and the micro-nano optical fiber are vertically placed and coupled in space to form a microcavity coupling system, and the microcavity coupling system is respectively connected to the polarization controller and the coupler; the output end of the coupler is divided into two paths, wherein the output light of one path is sequentially connected to the photodetector and the oscilloscope, and the output light of the other path is connected to the spectrometer; The adjustment module is used to continuously and finely adjust the output wavelength of the pump light, thereby realizing continuous tuning of the all-optical wavelength of the whispering gallery microcavity laser.

2. The system for realizing all-optical continuous wavelength tuning based on whispering gallery microcavity laser according to claim 1, characterized in that: The micro-nano optical fiber and the silica microcavity are placed vertically in space to achieve light field coupling, so as to excite the whispering gallery mode on the surface of the microcavity, thereby generating microcavity laser; wherein the micro-nano optical fiber is formed by taper of single-mode optical fiber, and has a diameter of 1-3 μm; the silica microcavity includes: a passive silica microcavity and a rare earth element doped silica microcavity; the microcavity shapes include spherical, bottle-shaped and ring-shaped, the sizes include 100-500 μm, and the quality factor is ≥10 7 .

3. The system for realizing all-optical continuous wavelength tuning based on whispering gallery microcavity laser according to claim 2, characterized in that: In the microcavity structure, pump light enters the silica microcavity through micro-nano optical fiber coupling, produces light amplification through the nonlinear effect of the light field or the stimulated radiation of rare earth ions, and finally produces the whispering gallery microcavity laser after multiple energy accumulation and mode selection in the whispering gallery microcavity.

4. The system for realizing all-optical continuous wavelength tuning based on whispering gallery microcavity laser according to claim 1, characterized in that: The working process of the adjustment module includes: the adjustment module outputs a triangular wave signal to control the pump source, so that the laser output wavelength of the pump source changes continuously with a wavelength accuracy of the order of picometers, so that the output wavelength of the whispering gallery microcavity laser generated by the pump source also undergoes a continuous red shift, thereby realizing the continuous tuning of the all-optical wavelength of the whispering gallery microcavity laser.

5. The system for realizing all-optical continuous wavelength tuning based on whispering gallery microcavity laser according to claim 4, characterized in that: The working principle of the all-optical wavelength continuous tuning includes: based on the premise that the pump light is coupled into the silica microcavity to generate the whispering gallery microcavity laser, when the pump laser coupled into the microcavity gradually accumulates, the temperature in the microcavity can be increased due to the photothermal effect of the silica material. At this time, the refractive index of the material and the size of the microcavity change, thereby causing the wavelength of the whispering gallery microcavity laser to redshift. The relationship between the wavelength redshift and the temperature satisfies: Where λ0 is the initial microcavity laser wavelength; is the coefficient of thermal expansion; is the thermo-optical coefficient; r represents the output wavelength of the final microcavity laser; ΔT represents the temperature change.

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