CN104035205A - High power pulse compression device based on helium-filled kagome optical fiber - Google Patents

Abstract

A high-power pulse compression device based on a helium-filled kagome fiber, including a laser diode, an isolator, a helium-filled kagome fiber, two half-wave plates, a polarization beamsplitter prism, and a single-channel grating compressor. The laser diode emits ps-level high-power pulses and injects them into the helium-filled kagome fiber through the isolator. Since the helium-filled kagome fiber has special optical properties and its loss threshold is high, high-power pulses can be transmitted in the kagome fiber. Transmission without damaging the kagome fiber, the high-power pulse output by the kagome fiber enters the first half-wave plate, and then enters the second half-wave plate after being reflected by the polarization beam splitter, and finally injected into the single-channel grating compressor for compression to achieve high Compression of pulses with power ps magnitude. In the experiment, we compressed the pulse with a width of 1ps to less than 480fs, the compressed pulse energy was 1μJ, the average output power was 10.2W, and the peak power was 1.7MW.

Description

A high-power pulse compression device based on a helium-filled kagome fiber

technical field

The invention belongs to the field of communication, and it is a kagome fiber device based on the coupling between a limited core mode and a cladding mode, and in particular relates to a kagome fiber filled with helium as a transmission medium to realize high-power pulses sent by a laser diode device for compression.

Background technique

Ultrashort pulses are widely used in the field of optical communication, and the compression of ps level pulses to fs level has always been the focus of researchers. T. Südmeyer and others achieved pulse compression at high power by using a solid photonic crystal fiber with a large mode field area. The pulse width of 760fs sent from the laser diode was compressed to 24fs, and the average power of the pulse after compression was 32W. The overall efficiency is 50%. C. J. Saraceno et al. realized the compression of high-power laser pulses by using a solid photonic crystal fiber amplifier. The pulse width can be compressed to 35 fs, and the pulse energy exceeds 3 μJ. These two compression devices are effective for the compression of μJ-level laser pulses. However, due to the self-focusing effect of standard fused silica solid fibers, pulses with peak powers exceeding 4 MW cannot directly use this fiber compression device. Therefore, in order to realize the compression of the pulse energy of 30μJ and the peak power of 25MW emitted by the laser diode with the best performance, it is necessary to find another compression device. Recently, S. H?drich et al. compressed the pulse width to 35fs with a pulse energy of 380μJ through a fiber amplifier device. Due to the large conduction mode power losses in the capillaries in this device, this technique cannot be used in optical fibers with small mode field diameters. Therefore, this device is only suitable for pulse energies of several hundred μJ and above.

In recent years, due to the emergence of kagome fiber, some new breakthroughs have been made in the research direction of pulse compression. Kagome fiber has unique optical properties. This kind of fiber has only an incomplete photonic band gap and does not intersect with the air line, but light can still be transmitted in the fiber. At the same time, it has a wide passband and low loss, and can meet long-term The application requirements of waveguide light or broadband light guidance can avoid defects such as narrow transmission bandwidth of photonic bandgap photonic crystal fiber, alternating light leakage of fundamental mode and interface mode, and has potential application value in the field of high-energy laser transmission.

Contents of the invention

The technical problem to be solved by the present invention is to provide a new high-power pulse compression device based on the low loss threshold of the compression device of the solid photonic crystal fiber, the serious superposition of the conduction mode in the fiber, and the large power loss of the pulse, so that the laser diode emits The high-power pulse can be injected into a single-channel grating compressor for compression after being transmitted in the kagome fiber, and finally the ps-level pulse emitted from the laser diode is compressed to the fs-level.

The present invention utilizes the high loss threshold, wide transmission bandwidth, low loss and small dispersion of the kagome fiber filled with helium gas, compared with some traditional pulse compression devices (such as: based on large mode field area solid photonic crystal fiber at high power) Pulse compression), the pulse compression device based on kagome fiber has the characteristics of high average power of compressed pulse, good pulse quality, compact structure, small volume, etc., and has attracted the attention of researchers.

Helium gas has a lower nonlinear refractive index than air and can compensate for the linear dispersion of the waveguide. The helium gas filled in the kagome fiber can also be used as a coolant, so that the pulse with a higher average power output by the laser diode can still be transmitted in the kagome fiber without damaging the fiber, which improves the loss threshold of the kagome fiber.

Technical scheme of the present invention:

A high-power pulse compression device based on a helium-filled kagome fiber, including a laser diode, an isolator, a helium-filled kagome fiber, two half-wave plates, a polarization beamsplitter prism, and a single-channel grating compressor. The high-energy pulse emitted by the laser diode passes through the isolator and then injects into the kagome fiber filled with helium gas, then passes through the first half-wave plate, the polarization beam splitter and the second half-wave plate in turn, and then enters the single-channel grating compressor.

The kagome optical fiber filled with helium is that two rubber air chambers are respectively sleeved on the two end faces of the kagome optical fiber, one air chamber is used to extract the air in the kagome optical fiber, and the other air chamber is filled with helium, squeezed The gas chamber fully infuses helium into the kagome fiber.

The half-wave plate changes the polarization direction of the high-power pulse output from the kagome fiber to be orthogonal to the previous pulse polarization direction.

The polarizing beam splitting prism is made of a pair of high-precision rectangular prisms glued together, and the slope of one of the prisms is coated with a silicon dioxide film with a polarizing beam splitting effect. Two beams of light.

The working principle of the device of the present invention is as follows:

The high-power laser pulse emitted by the laser diode is injected into the kagome fiber through the isolator. Due to the unique optical properties of the kagome fiber, the coupling between the high-order mode and the core mode in the fiber cladding can be suppressed, thereby reducing the pulse transmission loss. The helium gas filled in the kagome fiber can compensate the waveguide dispersion, and helium can also be used as a coolant, thus increasing the loss threshold of the kagome fiber, enabling the kagome fiber to transmit high-energy pulses.

The light pulse output from the kagome fiber passes through the first half-wave plate and then injects into the polarization splitter prism to convert the unpolarized light pulse into a linearly polarized light pulse, in which the P polarized light passes through completely, and the S polarized light is reflected at an angle of 45 ^° . The pulse is injected into the single-channel grating compressor through the second half-wave plate. After passing through the grating compressor, the high-power ps level pulse emitted by the laser diode can be compressed to the fs level.

Advantages and beneficial effects of the present invention:

The invention uses a kagome fiber filled with helium, and the helium can be used as a cooling agent in the pulse transmission process, thereby increasing the loss threshold of the kagome fiber. In the experiment, we compressed the pulse with a width of 1ps to less than 480fs, the compressed pulse energy was 1μJ, the average output power was 10.2W, and the peak power was 1.7MW. Such a compression device has potential application value in the field of optical communication.

Description of drawings

Fig. 1 Schematic diagram of the structure of a high-power pulse compression device based on a kagome fiber filled with helium;

In the figure: 1. Laser diode, 2. Isolator, 3. Kagome fiber, 4. Half-wave plate, 5. Polarization beam splitter, 6. Single-channel grating compressor, 7. Spectrometer.

Detailed ways

In order to better illustrate the purpose and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and examples.

Example 1

As shown in Figure 1, the present invention provides a high-power pulse compression device based on a kagome fiber, including a laser diode 1, an isolator 2, a kagome fiber 3, two half-wave plates 4, a polarization splitter prism 5, and a single-channel grating compressor 6 . The ps-level pulse emitted by the laser diode 1 is injected into the kagome fiber 3 filled with helium through the isolator 2. The kagome fiber used in the device is 30cm long. If a very long kagome fiber is used, it will lead to strong nonlinearity effect, greatly increasing the optical transmission loss; the mode field diameter is 25 μm, if the mode field diameter is too large, it will be impossible to achieve single-mode transmission, and the transmitted power will be greatly reduced. The kagome fiber 3 filled with helium has a higher loss threshold, so high-power pulses can be transmitted in the kagome fiber 3 without damaging the fiber. The pulse output from the kagome fiber 3 enters the first half-wave plate 4 and then passes through the polarization beam splitter prism 5 After reflection, it enters the second half-wave plate 4, and finally injects into the single-channel grating compressor 6, and the compressed pulse waveform is finally displayed on the spectrometer 7. The structure of kagome fiber 3 filled with helium is that two rubber air chambers are respectively sleeved on the two end faces of kagome fiber 3, one air chamber is used to extract the air in kagome fiber 3, and the other air chamber is filled with helium to squeeze out The plenum injects helium gas into the kagome fiber 3. The half-wave plate 4 changes the polarization direction of the high-power pulse output from the kagome fiber 3 to be orthogonal to the previous pulse polarization direction. The polarizing beam splitting prism 5 is made of a pair of high-precision right-angle prisms glued together. The slope of one of the prisms is coated with a polarizing beam splitting medium film.

The high-power laser pulse emitted by the laser diode 1 is injected into the kagome fiber 3 through the isolator. The kagome fiber 3 has unique optical properties, which can suppress the coupling between the high-order mode in the fiber cladding and the core mode, thereby reducing the transmission loss of the pulse. The helium gas filled in the kagome fiber 3 can compensate for waveguide dispersion, and at the same time, the helium gas can also be used as a coolant, thus increasing the loss threshold of the kagome fiber 3 and enabling the kagome fiber 3 to transmit high-energy pulses.

The light pulse output in the kagome fiber 3 passes through the first half-wave plate 4 and then injects into the polarization beam splitter 5 to convert the unpolarized light pulse into a linearly polarized light pulse, wherein the P polarized light passes through completely, and the S polarized light is reflected at an angle of 45 ^° . The pulse passes through the second half-wave plate 4 and is injected into the single-channel grating compressor 6. After passing through the grating compressor 6, the pulse with a width of 1 ps emitted by the laser diode 1 is compressed to less than 480 fs. The compressed pulse energy is 1 μJ, and the average The output power is 10.2W and the peak power is 1.7MW.

The loss threshold of kagome fiber 3 is high, the transmission bandwidth is wide, the loss is low, and the dispersion is small. On the one hand, helium can be used to compensate the dispersion of the waveguide, and on the other hand, it can also be used as a coolant, so that the loss threshold of kagome fiber 3 filled with helium With further improvement, high-power pulses can be transmitted, and finally the compression of high-power pulses can be realized.

Claims (5)

1. the high power pulse compression set based on filling the kagome optical fiber of helium, comprises the kagome optical fiber of laser diode, isolator, filling helium, two half-wave plates, polarization splitting prism, single pass gratings compressor; The high energy pulse that described laser diode sends is by injecting the kagome optical fiber of filling helium, then successively through entering single channel gratings compressor after first half-wave plate, polarization splitting prism and second half-wave plate after isolator.

2. device according to claim 1, the kagome optical fiber that it is characterized in that described filling helium is two rubber air chambers to be enclosed within respectively to two end faces of kagome optical fiber, an air chamber is used for extracting out the air in kagome optical fiber, in another air chamber, fill helium, extruding air chamber injects kagome optical fiber by helium.

3. device according to claim 1 and 2, is characterized in that the long 30cm of kagome optical fiber of described filling helium; Mode field diameter is 25 μ m.

4. install according to claim 1, it is characterized in that first described half-wave plate is that the change of polarized direction of the high power pulse of exporting is become to prepulse polarization direction quadrature with it from kagome optical fiber; Second described half-wave plate is that the change of polarized direction that makes transmission cross the pulse of polarization splitting prism becomes prepulse polarization direction quadrature with it by after polarization splitting prism reflection.

5. device according to claim 1, it is characterized in that described polarization splitting prism is to be formed by a pair of high precision right-angle prism gummed, on the inclined-plane of one of them prism, be coated with polarization spectro deielectric-coating, its effect is that a branch of incident light is divided into the mutually perpendicular two-beam in the direction of propagation.