A tunable laser with short cavity length

Abstract

The present invention provides a short-cavity tunable laser, comprising a tunable optical filter, a semiconductor optical amplifier, a first positioning sleeve, and a second positioning sleeve. The tunable optical filter is provided with a first input ferrule and a first output ferrule, and the semiconductor optical amplifier is provided with a second input ferrule, a second output ferrule, and a target output terminal. The first input ferrule and the second output ferrule are inserted into the first positioning sleeve, with the end of the first input ferrule facing the end of the second output ferrule. The first positioning sleeve is filled with a refractive index matching fluid. The second input ferrule and the first output ferrule are inserted into the second positioning sleeve, with the end of the second input ferrule facing the end of the first output ferrule. The second positioning sleeve is filled with a refractive index matching fluid. The connection scheme of the ferrules and the positioning sleeves effectively shortens the cavity length, achieves a higher scanning frequency, and facilitates equipment replacement and debugging.

Description

Technical Field

[0001] The present invention relates to the field of optical devices, in particular to a tunable laser with a short cavity length. Background Art

[0002] Single-frequency tunable lasers and high-speed wavelength swept lasers are widely used in many fields, such as optical coherence tomography (OCT), biochemical spectroscopy, fiber optic sensing applications, and optical communications. To achieve a wide range of commercial applications, building a ring cavity based on filters and semiconductor optical amplifiers is an important way to achieve swept lasers.

[0003] In practice, the components that make up a ring cavity, including semiconductor optical amplifiers, optical isolators, couplers, and optical filters, are typically connected using fiber fusion splicing, making it difficult to create a shorter ring cavity. The shorter the cavity length of a short ring cavity, the higher the scanning frequency it can support. Therefore, building a sufficiently short ring cavity is an important prerequisite for producing high-speed frequency-swept lasers. Summary of the Invention

[0004] The object of the present invention is to provide a tunable laser which can realize a higher scanning frequency by utilizing a short cavity length.

[0005] In order to achieve the object of the present invention, the present invention provides a tunable laser with a short cavity length, comprising:

[0006] A tunable optical filter, wherein the tunable optical filter is provided with a first input ferrule and a first output ferrule;

[0007] A semiconductor optical amplifier device, the semiconductor optical amplifier device is provided with a second input ferrule, a second output ferrule and a target output end;

[0008] A first positioning sleeve, into which the first input ferrule and the second output ferrule are inserted, with the end of the first input ferrule facing the end of the second output ferrule, and the first positioning sleeve is filled with a refractive index matching liquid;

[0009] The second positioning sleeve is filled with a refractive index matching liquid. The second input ferrule and the first output ferrule are inserted into the second positioning sleeve. The end of the second input ferrule is opposite to the end of the first output ferrule.

[0010] A further solution is that the first positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve, and the second positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve.

[0011] A further solution is that the tunable optical filter is a fiber Fabry-Perot filter.

[0012] In order to achieve the object of the present invention, the present invention can also provide a tunable laser with a short cavity length, comprising:

[0013] A tunable optical filter, wherein the tunable optical filter is provided with a first input ferrule and a first output ferrule;

[0014] A semiconductor optical amplifier device, wherein the semiconductor optical amplifier device is provided with a second input ferrule and a second output ferrule;

[0015] a first isolator, the first isolator being provided with a third input ferrule, a third output ferrule and a target output end;

[0016] A first positioning sleeve, into which the first input ferrule and the second output ferrule are inserted, with the end of the first input ferrule facing the end of the second output ferrule, and the first positioning sleeve is filled with a refractive index matching liquid;

[0017] A second positioning sleeve, into which the third input ferrule and the first output ferrule are inserted, with the end of the third input ferrule facing the end of the first output ferrule, and the second positioning sleeve is filled with a refractive index matching liquid;

[0018] The second input ferrule and the third output ferrule are inserted into the third positioning sleeve, the end of the second input ferrule is opposite to the end of the third output ferrule, and the third positioning sleeve is filled with a refractive index matching liquid.

[0019] A further solution is that the first positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; the second positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; and the third positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve.

[0020] A further solution is that the tunable optical filter is a fiber Fabry-Perot filter.

[0021] In order to achieve the object of the present invention, the present invention can also provide a tunable laser with a short cavity length, comprising:

[0022] A tunable optical filter, wherein the tunable optical filter is provided with a first input ferrule and a first output ferrule;

[0023] A semiconductor optical amplifier device, wherein the semiconductor optical amplifier device is provided with a second input ferrule and a second output ferrule;

[0024] a first isolator, the first isolator being provided with a third input ferrule, a third output ferrule and a target output end;

[0025] A second isolator, the second isolator being provided with a fourth input ferrule and a fourth output ferrule;

[0026] a first positioning sleeve, into which the first input ferrule and the fourth output ferrule are inserted, with the end of the first input ferrule facing the end of the fourth output ferrule, and the first positioning sleeve is filled with a refractive index matching liquid;

[0027] A second positioning sleeve, into which the third input ferrule and the first output ferrule are inserted, with the end of the third input ferrule facing the end of the first output ferrule, and the second positioning sleeve is filled with a refractive index matching liquid;

[0028] a third positioning sleeve, into which the second input ferrule and the third output ferrule are inserted, with the end of the second input ferrule facing the end of the third output ferrule, and the third positioning sleeve is filled with a refractive index matching liquid;

[0029] A fourth positioning sleeve, into which the fourth input ferrule and the second output ferrule are inserted, with the end of the fourth input ferrule facing the end of the second output ferrule, and the fourth positioning sleeve is filled with a refractive index matching liquid.

[0030] A further solution is that the first positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; the second positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; the third positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; and the fourth positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve.

[0031] A further solution is that the tunable optical filter is a fiber Fabry-Perot filter.

[0032] A further solution is that the first isolator is an isolator with a reflection output end, and the target output end is located at the reflection output end.

[0033] The beneficial effect of the present invention is that, based on the existing fusion splicing technology, it is difficult to shorten the cavity length of the annular cavity due to the need to use a fiber fusion splicer and a fiber clamp for fusion splicing. However, this case does not use fusion splicing for optical fiber coupling connection. The connection of the various components of the tunable laser uses two cores to achieve optical signal coupling. When connecting, the two cores are inserted into the positioning sleeve and matched with the refractive index matching liquid filled therein, thereby improving the optical coupling efficiency. Since the production of the core is relatively simple, the optical fiber with the coating removed is generally cut to the appropriate length, loaded into the ceramic core, and finally moderately polished. In this way, not only the optical fiber length is controllable and the assembly and production are convenient, but also the length of the connected optical fiber can be effectively controlled or locked, ultimately achieving effective shortening of the cavity length and achieving a higher scanning frequency. In addition, the connection scheme of the core and the positioning sleeve is also convenient for device testing, replacement and scheme change, and the core can be reused multiple times, which is not only low in cost but also easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1It is a structural diagram of the first embodiment of the tunable laser of the present invention.

[0035] Figure 2 1 is a structural diagram of the ferrule and positioning sleeve in the first embodiment of the tunable laser of the present invention.

[0036] Figure 3 It is a cross-sectional view of the ferrule and the positioning sleeve in the first embodiment of the tunable laser of the present invention.

[0037] Figure 4 It is a structural diagram of the second embodiment of the tunable laser of the present invention.

[0038] Figure 5 It is a structural diagram of the third embodiment of the tunable laser of the present invention.

[0039] Figure 6 4 is a structural diagram of a tunable laser according to a fourth embodiment of the present invention.

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0041] The first embodiment of the tunable laser:

[0042] Reference Figures 1 to 3 The tunable laser includes a tunable optical filter 11, a semiconductor optical amplifier 12, a first isolator 13, a second isolator 14, a first positioning sleeve 21, a second positioning sleeve 22, a third positioning sleeve 23, and a fourth positioning sleeve 24. The tunable optical filter 11 is a fiber Fabry-Perot filter and includes a piezoelectric ceramic 15, a fiber ferrule 112, and a fiber ferrule 113. The ends of the fiber ferrule 112 and the fiber ferrule 113 are arranged relative to each other. The specific structure and operating principle can be found in the structure disclosed in CN109557617A entitled "Tunable Filter". By energizing the piezoelectric ceramic 15, the spacing between the fiber ferrules can be finely and quickly adjusted. By using precise or fast spacing adjustment, the filter can have a wide filter adjustment range and achieve fast frequency sweeping.

[0043] The tunable optical filter 11 is equipped with a first input ferrule 31 and a first output ferrule 32. The optical fiber ferrule 113 is connected to the first input ferrule 31 via an optical fiber 311, and the optical fiber ferrule 112 is connected to the first output ferrule 32 via an optical fiber 321. The input and output ferrules have the same structure. Taking the first input ferrule 31 as an example, the first input ferrule 31 includes a ceramic ferrule 313, a handle 312, and an optical fiber 311. The ceramic ferrule 313 has a capillary hole axially arranged therein, into which the optical fiber 311 extends. The handle 312 is located on the periphery of the optical fiber 311.

[0044] The semiconductor optical amplifier device 12 is referred to as SOA. The semiconductor optical amplifier device 12 is provided with a second input ferrule 33 and a second output ferrule 34. The second input ferrule 33 is connected to the semiconductor optical amplifier device 12 through an optical fiber 331, and the second output ferrule 34 is connected to the semiconductor optical amplifier device 12 through an optical fiber 341.

[0045] The first isolator 13 is an isolator with a reflective output port. For example, the "Polarization Insensitive Tap Isolator" from Zhuhai Guangku Technology Co., Ltd. can be used. Isolators with reflective output ports are commonly known and used. The first isolator 13 is equipped with a third input ferrule 35, a third output ferrule 36, and a target output port 131, which is located at the reflective output port. The third input ferrule 35 and the third output ferrule 36 are each connected to the first isolator 13 via optical fibers.

[0046] The second isolator 14 is provided with a fourth input ferrule 37 and a fourth output ferrule 38, which are respectively connected to the second isolator 14 via optical fibers. The first isolator 13 and the second isolator 14 are both optical isolators, which can achieve unidirectional light transmission and reverse blocking. The first isolator 13 is provided with a preset ratio of transflective mirrors or transflective films, which can reflect a certain proportion of light to the target output end 131, and then the target light is output.

[0047] The first, second, third, and fourth positioning sleeves 21, 22, 23, and 24 all utilize C-shaped ceramic sleeves. Taking the first positioning sleeve 21 as an example, the first positioning sleeve 21 is axially perforated, and a groove 211 is provided on the peripheral wall of the first positioning sleeve 21. Alternatively, the aforementioned positioning sleeves may utilize V-shaped ceramic sleeves to achieve ferrule positioning.

[0048] The first input ferrule 31 and the fourth output ferrule 38 are inserted into the first positioning sleeve 21 , with the end of the first input ferrule 31 facing the end of the fourth output ferrule 38 . The first positioning sleeve 21 is filled with a refractive index matching liquid.

[0049] The third input ferrule 35 and the first output ferrule 32 are inserted into the second positioning sleeve 22 , with the end of the third input ferrule 35 facing the end of the first output ferrule 32 . The second positioning sleeve 22 is filled with a refractive index matching liquid.

[0050] The second input ferrule 33 and the third output ferrule 36 are inserted into the third positioning sleeve 23 , with the end of the second input ferrule 33 facing the end of the third output ferrule 36 . The third positioning sleeve 23 is filled with a refractive index matching liquid.

[0051] The fourth input ferrule 37 and the second output ferrule 34 are inserted into the fourth positioning sleeve 24, with the end of the fourth input ferrule 37 facing the end of the second output ferrule 34. The fourth positioning sleeve 24 is filled with a refractive index matching fluid. This facing end position of the input and output ferrules, combined with the refractive index matching fluid, allows light to be efficiently coupled from the input ferrule to the output ferrule.

[0052] The above structure forms a ring cavity, and under the action of two isolators, light can only pass through the semiconductor optical amplifier device in one direction, such as Figure 1 Transmission is counterclockwise as shown. During the initial startup of the ring cavity, the spontaneously emitted light from the semiconductor optical amplifier passes through the isolator and then reaches the optical filter. The narrow linewidth spectrum selected by the filter passes through the filter and is then incident on the first isolator 13. A certain amount of reflected light is output from the target output port 131, and a certain proportion of the transmitted light is output to the semiconductor optical amplifier 12. The semiconductor optical amplifier amplifies the light intensity of this spectrum. The amplified light then passes through the second isolator 14, the optical filter, and the first isolator 13 before returning to the semiconductor optical amplifier 12 for further amplification. This cycle continues until the ring cavity loss and the optical amplifier gain are equal. The ring cavity loss includes the coupling loss of the light beam and the proportion of the output light. By controlling the piezoelectric ceramic, the optical filter can be driven to perform frequency sweeping, allowing the ring cavity to output a swept frequency optical signal.

[0053] The first embodiment of the tunable laser adopts the fixing method of core docking and positioning sleeve. Since fiber fusion is not used, the fiber length between devices can be greatly reduced, the cavity length can be accurately controlled or shortened, and the scanning frequency that can be supported is higher.

[0054] The second embodiment of the tunable laser:

[0055] Reference Figure 4 On the basis of the first embodiment, in order to pursue the shortest possible cavity length, the arrangement of the components and the length of the optical fiber can be further shortened, that is, the optical fibers 311, 321, 331, and 341 are arranged in a curved manner, and the above-mentioned optical fibers are placed within the maximum bending radius under the required light transmission state. The length of the optical fibers at both ends of the isolator is also shortened as much as possible, thereby effectively shortening the cavity length, so that the ring cavity of this embodiment can successfully output a swept-frequency laser with a scanning speed of 500 kHz.

[0056] The third embodiment of the tunable laser:

[0057] Reference Figure 5Based on the above embodiment, the isolator in the first embodiment is removed, and a target output terminal 121 is provided on the semiconductor optical amplifier device 12. The specific layout of the semiconductor optical amplifier device 12 can be found in the disclosure of CN111668694A entitled Tunable Laser. By using transmissive and reflective elements with a preset ratio, both co-directional amplified output and reflective reverse amplified output can be achieved. The input and output terminals of the semiconductor optical amplifier device are both equipped with isolators.

[0058] The tunable optical filter 11 can adopt an optical fiber Fabry-Perot filter. The tunable optical filter 11 is provided with a first input ferrule 41 and a first output ferrule 42. The semiconductor optical amplifier device 12 is provided with a second input ferrule 43, a second output ferrule 44 and a target output end 121. The first input ferrule 41 and the second output ferrule 44 are inserted into a first positioning sleeve 45, with the end of the first input ferrule 41 facing the end of the second output ferrule 44. The first positioning sleeve 45 is filled with a refractive index matching liquid. The second input ferrule 43 and the first output ferrule 42 are inserted into a second positioning sleeve 46, with the end of the second input ferrule 43 facing the end of the first output ferrule 42. The second positioning sleeve 46 is filled with a refractive index matching liquid.

[0059] Through the core docking and positioning sleeve fixing method of this case, as well as the shortest arrangement of optical fibers, it is also possible to build a ring cavity with a sufficiently short cavity length, and then output a swept laser with a high scanning frequency.

[0060] Fourth embodiment of tunable laser:

[0061] Reference Figure 6Based on the first embodiment, the isolator 14 in the first embodiment is removed. The tunable laser includes a tunable optical filter 11, a first isolator 13, a first positioning sleeve 59, a second positioning sleeve 57, and a third positioning sleeve 58. The tunable optical filter 11 is provided with a first input ferrule 51 and a first output ferrule 52, a semiconductor optical amplifier 12, and a semiconductor optical amplifier 12 is provided with a second input ferrule 55 and a second output ferrule 56. The first isolator 13 is provided with a third input ferrule 54, a third output ferrule 55, and a target output terminal. The first input ferrule 51 and the second output ferrule 56 are inserted into the target output terminal. The first positioning sleeve 59 is inserted into the first positioning sleeve 59, with the end of the first input ferrule 51 facing the end of the second output ferrule 56, and the first positioning sleeve 59 is filled with refractive index matching liquid. The third input ferrule 54 and the first output ferrule 52 are inserted into the second positioning sleeve 57, with the end of the third input ferrule 54 facing the end of the first output ferrule 52, and the second positioning sleeve 57 is filled with refractive index matching liquid. The second input ferrule 55 and the third output ferrule 55 are inserted into the third positioning sleeve 58, with the end of the second input ferrule 55 facing the end of the third output ferrule 55, and the third positioning sleeve 58 is filled with refractive index matching liquid.

[0062] The above embodiments can also be used to construct a ring cavity with a sufficiently short cavity length, thereby being able to output a swept laser with a high scanning frequency.

[0063] As can be seen above, by significantly reducing the length of the ring cavity, discrete single-frequency laser tuning and support for higher-speed swept-frequency lasers are effectively achieved. Of course, the above embodiment is only a preferred embodiment of this case, and in actual use, more variations are possible. For example, the filter can adopt other forms of tunable filters, as long as the filtering is adjustable, and the form of the isolator can also be adjusted according to actual needs. These variations are all within the scope of protection of the present invention.

Claims

1. A tunable laser with a short cavity length, characterized in that: include: A tunable optical filter, wherein the tunable optical filter is provided with a first input ferrule and a first output ferrule; A semiconductor optical amplifier device, wherein the semiconductor optical amplifier device is provided with a second input ferrule and a second output ferrule; a first isolator, the first isolator being provided with a third input ferrule, a third output ferrule and a target output end; a second isolator, the second isolator being provided with a fourth input ferrule and a fourth output ferrule; a first positioning sleeve, into which the first input ferrule and the fourth output ferrule are inserted, with an end of the first input ferrule facing an end of the fourth output ferrule, and the first positioning sleeve is filled with a refractive index matching liquid; a second positioning sleeve, into which the third input ferrule and the first output ferrule are inserted, with an end of the third input ferrule facing an end of the first output ferrule, and the second positioning sleeve is filled with a refractive index matching liquid; a third positioning sleeve, into which the second input ferrule and the third output ferrule are inserted, with an end of the second input ferrule facing an end of the third output ferrule, and the third positioning sleeve is filled with a refractive index matching liquid; a fourth positioning sleeve, into which the fourth input ferrule and the second output ferrule are inserted, with an end of the fourth input ferrule facing an end of the second output ferrule, and the fourth positioning sleeve is filled with a refractive index matching liquid; The first isolator is an isolator with a reflection output end, and the target output end is located at the reflection output end; The tunable optical filter includes a piezoelectric ceramic, a first optical fiber ferrule, and a second optical fiber ferrule. The ends of the first optical fiber ferrule and the second optical fiber ferrule are arranged opposite to each other. The first optical fiber ferrule is connected to the first input ferrule via a first optical fiber, the second optical fiber ferrule is connected to the first output ferrule via a second optical fiber, the second input ferrule is connected to the semiconductor optical amplifier device via a third optical fiber, and the second output ferrule is connected to the semiconductor optical amplifier device via a fourth optical fiber. The first optical fiber, the second optical fiber, the third optical fiber, and the fourth optical fiber are arranged in a curved manner, and the first optical fiber, the second optical fiber, the third optical fiber, and the fourth optical fiber are within a maximum bending radius under a required light transmission state, and the tunable laser can output a swept frequency laser with a scanning speed of up to 500 kHz.

2. The tunable laser according to claim 1, wherein: The first positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; The second positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; The third positioning sleeve adopts a C-shaped ceramic sleeve or a V-shaped ceramic sleeve; The fourth positioning sleeve is a C-shaped ceramic sleeve or a V-shaped ceramic sleeve.

3. The tunable laser according to claim 1, wherein: The tunable optical filter is an optical fiber Fabry-Perot filter.

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