CN105390911A - All-fiber 2mum-waveband dual wavelength gap-adjustable thulium-doped fiber laser - Google Patents

Abstract

An all-fiber 2μm-band dual-wavelength interval adjustable thulium-doped fiber laser belongs to the field of laser manufacturing technology. In order to solve the defect that the dual-wavelength interval in the 2μm-band dual-wavelength fiber laser is relatively short and susceptible to external interference, the laser diode pumping source of the laser and The optical fiber amplifier is connected, the output end of the optical fiber amplifier is connected to the wavelength division multiplexer, the wavelength division multiplexer is connected to the thulium-doped fiber, the thulium-doped fiber is connected to the 50:50 broadband coupler, and the 50:50 broadband coupler is connected to the multimode The interference filter is connected, and the 50:50 broadband coupler is connected with the multimode interference filter, so that the Sagnac ring and the multimode interference filter are cascaded to form a composite filtering structure; the 50:50 broadband coupler is connected with the input end of the isolator ; The output end of the isolator is connected to the 90:10 broadband coupler, the wavelength division multiplexer is connected to the 90:10 broadband coupler to form a ring cavity, and the 90:10 broadband coupler performs 2μm dual-wavelength output.

Description

All-fiber 2μm-band dual-wavelength spacing tunable Thulium-doped fiber laser

technical field

The invention relates to an all-fiber structure 2μm band dual-wavelength interval tunable laser based on a composite multimode interference filter, which belongs to the technical field of laser manufacturing. The laser can be applied to many fields such as microwave photonics, remote sensing, and laser radar.

Background technique

2μm band fiber laser is one of the most promising laser technologies at present, and has a wide range of applications in laser medical treatment, gas detection, free space optical communication, etc. Dual-wavelength fiber lasers operating in the 2μm band have gradually attracted people's attention because of their unique advantages in microwave photonics and optical device detection.

The Chinese patent "Dual-Wavelength Tunable Thulium-doped Fiber Laser", the publication number is CN101859975, as shown in Figure 1, the structure of the device is as follows:

A dual-wavelength tunable rust-doped fiber laser consists of a first pumping source 1, a second pumping source 2, a first pumping light focusing lens 3, a second pumping light focusing lens 4, a first dichroic mirror 5, and a second pumping light focusing lens 4. Dichroic mirror 6, thulium-doped fiber 7, laser collimator lens 8 at the output end, laser collimator lens 9 at the feedback end, the first reflective volume Bragg grating VBGl10, the second reflective volume Bragg grating VBG211 and the high reflection of broadband dielectric film mirror 12. The first pump light focusing lens 3, the first dichroic mirror 5, the rust-doped optical fiber 7, the second dichroic mirror 6, the second pump light focusing lens 4 and the first pump light focusing lens 4 are sequentially placed on the horizontal optical path of the first pump source 1. Two pumping sources 2; an output end laser collimator lens 8 is placed on the vertical optical path facing the first dichroic mirror 5; a reflective end laser collimating lens 9, a reflective body are placed on the vertical optical path facing the second dichroic mirror 6 Bragg grating 10, reflective volume Bragg grating 11 and broadband dielectric film high reflection mirror 12. Two volume Bragg gratings VBG110 and VBG211 are used as resonant cavity end reflectors, and the dielectric film mirror 12 is used as an auxiliary component to help realize the angle tuning of the VBG. The technical scheme adopts a bidirectional pumping structure, and by adjusting two volume Bragg gratings VBG110 and VBG211, a dual-wavelength interval adjustable by 50nm is finally obtained.

However, since the 2μm band dual-wavelength fiber laser adopts a volume Bragg grating structure, the performance of the volume Bragg grating is limited by the grating manufacturing process, which limits the tuning range of the dual-wavelength interval, and the cost of the grating is high, which is not conducive to the development of dual-wavelength fiber lasers. . At the same time, the design of non-full fiber structure makes the fiber need to be coupled with various functional devices in free space, which requires adding a certain number of lenses and optical path alignment adjustment mechanisms, so it is susceptible to external environmental interference and has poor practicability.

Contents of the invention

In order to solve the defect that the dual-wavelength interval in the prior art 2μm band dual-wavelength fiber laser is relatively short and susceptible to external interference, the present invention proposes an all-fiber structure 2μm dual-wavelength interval tunable laser based on a composite multimode interference filter. The minimum interval of the obtained dual-wavelength output is 3nm, and the maximum interval is 80nm, and the side mode suppression is relatively high, about 60dB, the wavelength output is stable, the tuning is simple, and the manufacturing cost is low.

The present invention takes following technical scheme:

An all-fiber 2μm band dual-wavelength interval adjustable thulium-doped fiber laser is characterized in that the laser is composed of a laser diode pump source, an optical fiber amplifier, a wavelength division multiplexer, a thulium-doped fiber, a 50:50 broadband coupler, and a multimode interference It is composed of filter, isolator and 90:10 broadband coupler; the laser diode pump source is connected to the fiber amplifier, the output port of the fiber amplifier is connected to the a terminal of the wavelength division multiplexer, and the c terminal of the wavelength division multiplexer is connected to the doped One end of the thulium fiber is connected, the other end of the thulium-doped fiber is connected to the d end of the 50:50 broadband coupler, the f end of the 50:50 broadband coupler is connected to one end of the multimode interference filter, and the g end of the 50:50 broadband coupler is connected to the The other end of the multi-mode interference filter is connected, so that the Sagnac ring is cascaded with the multi-mode interference filter to form a composite filter structure; the e end of the 50:50 broadband coupler is connected to the input end of the isolator; the output end of the isolator is connected to the The k terminal of the 90:10 broadband coupler is connected, the b terminal of the wavelength division multiplexer is connected with the h terminal of the 90:10 broadband coupler to form a ring cavity, and the i terminal of the 90:10 broadband coupler performs 2μm dual wavelength output.

The first output port i of the 90:10 broadband coupler is a 10% output port, and the second output port h is a 90% output port.

The beneficial effects of the present invention are:

The present invention outputs a 2μm-band thulium-doped fiber laser with adjustable dual-wavelength intervals, which can obtain stable laser output with a minimum interval of 3nm and a maximum interval of 80nm. The tuning range (80nm) is 1.6 times that of the best result found so far (tuning range of dual wavelength interval 50nm). It overcomes the characteristics that the existing 2μm band dual-wavelength fiber laser is not all-fiber, is easily disturbed by the external environment, has a narrow tuning range, and has high cost. First of all, the tunable dual-wavelength output in the 2μm band has a broad application prospect in the fields of microwave photonics and optical device detection. Secondly, the present invention adopts Sagnac ring and multi-mode interference filter to be cascaded, and the composite filter obtained can produce dual-wavelength interval tunable laser output, the dual-wavelength interval tuning range is large, and the side-mode suppression ratio is high. Finally, the present invention adopts an all-fiber structure, which has low loss, stable performance, and is easy to integrate with an optical fiber system. And the cost is low, with high cost performance.

Description of drawings

FIG. 1 is a schematic diagram of a prior art dual-wavelength thulium-doped fiber laser.

Fig. 2 is a schematic structural diagram of a thulium-doped fiber laser with adjustable dual-wavelength spacing of the present invention.

Fig. 3 is a schematic structural diagram of the stress-related multimode interference filter of the present invention.

4-7 are spectrum diagrams of the present invention with adjustable dual-wavelength intervals.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings.

As shown in Figure 2, the 2 μm band dual-wavelength interval adjustable thulium-doped fiber laser is composed of a laser diode pump source 13 with a wavelength of 1565nm, an erbium-doped fiber amplifier 14, and a 1560/2000nm wavelength division multiplexer 15 ("/" means "and"), single-clad thulium-doped fiber 16, 50:50 broadband coupler in 2 μm band 17, stress-dependent multimode interference filter 18, isolator in 2 μm band 19, 90:10 broadband coupler in 2 μm band 20 are connected to form a ring laser cavity.

The laser diode pumping source 13 is connected to the erbium-doped fiber amplifier 14, and the pumping power is set to 30dBm. The output end of the erbium-doped fiber amplifier 14 is connected to the a-end of the wavelength division multiplexer 15 to inject pump light into the ring cavity. The c-end of the wavelength division multiplexer 15 is connected to one end of the thulium-doped optical fiber 16, thereby generating a 2 μm gain signal. The other end of the thulium-doped optical fiber 16 is connected with the d end of the 50:50 broadband coupler 17, the f end of the 50:50 broadband coupler 17 is connected with one end of the multimode interference filter 18, and the g end of the 50:50 broadband coupler 17 It is connected to the other end of the multimode interference filter 18, so that the Sagnac ring is cascaded with the multimode interference filter 18 to form a composite filtering structure, and the dual wavelength interval is realized by twisting and pressing the multimode interference filter 18 in the composite filtering structure 3nm-80nm output control. The e terminal of the 50:50 broadband coupler 17 is connected to the input terminal of the isolator 19, thereby ensuring the single-phase operation of the optical signal in the resonant cavity. The output end of the isolator 19 is connected to the k end of the 90:10 broadband coupler 20 . The b end of the wavelength division multiplexer 15 is connected to the h end of the 90:10 broadband coupler 20, the i end of the 90:10 broadband coupler 20 is a 10% end for laser output, and the h end is a 90% end for providing light feedback. In this way, a fiber laser with a ring cavity structure is formed, and all components are connected by optical fiber fusion.

As shown in Figure 3, the structure of the multimode interference filter 18 is: the multimode optical fiber 18-1 is directly embedded in the V-shaped groove of the fiber rotator 18-3, and the fiber locker 18-4 is arranged on the fiber rotator 18- 3 Lock the multimode fiber 18-1 on both sides, and set the rotating screw 18-2 above the fiber rotator 18-3 to apply stress to the multimode fiber 18-1, and turn the fiber rotator 18-3 to twist the multimode fiber. The optical fiber 18-1 changes the effective length of the multimode optical fiber 18-1, thereby changing the interference peak value and realizing tunable filtering;

As shown in Figure 4-7, when the pump power is set to 30dBm, the polarization state can be controlled by twisting and pressing the multimode interference filter 18 in the composite filter structure, thereby realizing the control of the output of the dual wavelength interval 3nm-80nm . The i-side laser light of the 90:10 broadband coupler 20 is measured by a 2 μm band fiber optic spectrum analyzer and a 2 μm band optical power meter.

Claims (2)

1. An all-fiber 2 μm band dual-wavelength interval adjustable thulium-doped fiber laser, characterized in that the laser consists of a laser diode pump source (13), an optical fiber amplifier (14), a wavelength division multiplexer (15), and a thulium-doped fiber laser. (16), 50:50 broadband coupler (17), multimode interference filter (18), isolator (19) and 90:10 broadband coupler (20); laser diode pump source (13) and optical fiber The amplifier (14) is connected, and the output end of the optical fiber amplifier (14) is connected with the a end of the wavelength division multiplexer (15), and the c end of the wavelength division multiplexer (15) is connected with one end of the thulium-doped optical fiber (16). The other end of the thulium fiber (16) is connected to the d end of the 50:50 broadband coupler (17), the f end of the 50:50 broadband coupler (17) is connected to one end of the multimode interference filter (18), and the 50:50 broadband The g end of the coupler (17) is connected to the other end of the multimode interference filter (18), so that the Sagnac ring and the multimode interference filter (18) are cascaded to form a composite filtering structure; the 50:50 broadband coupler (17 ) is connected to the input terminal of the isolator (19); the output terminal of the isolator (19) is connected to the k terminal of the 90:10 broadband coupler (20), and the b terminal of the wavelength division multiplexer (15) is connected to the The h terminals of the 90:10 broadband coupler (20) are connected to form a ring cavity, and the i terminal of the 90:10 broadband coupler (20) outputs 2 μm dual wavelengths. 2. the all-fiber 2 μm band double-wavelength interval adjustable thulium-doped fiber laser according to claim 1, characterized in that: the first output i of the 90:10 broadband coupler (20) is a 10% output end, The second output terminal h is a 90% output terminal.