Ultra narrow line width laser generation device

Abstract

To provide an ultra narrow line width laser generation device.SOLUTION: An ultra narrow line width laser generation device contains: a light self-implantation lock loop; and an ultra stability cavity phase lock loop. The light self-implantation lock loop improves a quality factor of a laser resonance cavity, and narrows a line width. The ultra stability cavity phase lock loop locks a phase of an optical signal in a light self-implantation, realizes a synchronization of a frequency and an optical resonance cavity of a laser device, reduces a frequency noise of the laser device by a driving current of a feedback control laser device to improve a line width narrowing ratio of the laser device, and avoids the generation of a mode hopping phenomenon by a drift of the frequency of the laser device in order to perform a stable control against the frequency of the laser device of the ultra stability cavity phase lock loop, to improve a stability of a system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the field of optoelectronics, and in particular to an ultra-narrow linewidth laser generating device. [Background technology]

[0002] The full name of a laser is stimulated emission of light, which means that particles at high energy levels emit light that is outside the body. photons are excited by the electrons, which transition to lower energy levels and produce light with optical properties that closely match those of the excited photons. This refers to the emission of a child beam. Therefore, lasers are monochromatic and It has advantages such as directivity and is used in optical fiber communications, laser radar, industrial device processing, medical applications, etc. In the ideal case, the laser emits only stimulated emission. The lost energy of the higher energy level atoms is replenished in the induction process. At the same time, the generated light wave overlaps with the original light wave in an interference manner, resulting in a light wave in the resonant cavity. To keep the amplitude constant throughout, the line width should be as close to zero as possible. However, due to the effect of spontaneous emission, the stimulated emission gain in the laser is The loss is slightly smaller than the total loss, and the generated incoherent light wave overlaps with the coherent light due to stimulated emission. This leads to broadening of the laser linewidth. Due to factors such as the boundary, frequency drift and phase jitter inevitably occur in laser devices. When this is reflected in the power spectrum, it is called an expansion. Taking coherent optical communication as an example, the expansion of the laser linewidth This will cause a deterioration of the signal-to-noise ratio at the receiving end, further affecting the quality of communication. Therefore, narrow-linewidth lasers are an essential part of laser applications. Mature commercial distributed feedback semiconductor lasers have linewidths on the order of megahertz. This is already sufficient for general applications, but some precision optical measurements and high-quality It is still insufficient for applications such as microwave photon signal generation. The device is very expensive and significantly increases the cost of the system. hopes that other external structures can narrow the laser linewidth.

[0003] The optical self-injection locking technique is a method that can narrow the linewidth of a laser. If a part of the output light of the laser is coupled into the laser by a circulator, the laser Therefore, it is possible to realize a narrower linewidth of the laser device. The system has a very simple structure and can achieve a relatively high linewidth narrowing ratio. However, the self-injection approach substantially increases the loop length of the resonant cavity. This corresponds to obtaining a higher resonant cavity quality factor (Q value) by Therefore, a relatively long loop length introduces more phase jitter and reduces the freedom This causes a reduction in the spectral range, and more longitudinal modes cannot satisfy the oscillation conditions of the oscillator. This leads to a relatively low side mode suppression ratio, which greatly reduces the frequency stability of the laser. To do this, the researchers use a single narrow-band optical fiber in the feedback loop. We suggest that you add a filter to filter out unnecessary modes. The most commonly seen narrowband filters are those based on Fabry-Perot resonant cavities, grating resonators, etc. These include cavities, echo wall mode resonant cavities, etc. However, they are relatively small. The small free spectral range also places higher demands on the quality factor of narrowband filters. We propose a method to improve the linewidth narrowing rate of the optical self-injection locking by strengthening the feedback injection light. approaches saturation, typically on the order of several hundred to several thousand times. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above, the present invention provides an ultra-narrow linewidth laser generating device, which is optically self-injected. It has a higher line narrowing ratio and lower frequency noise than the conventional locking ... The use of optical resonant cavities is avoided, reducing system cost. [Means for solving the problem]

[0005] The ultra-narrow linewidth laser generator is based on an optical self-injection locked loop and an ultra-stable cavity phase locked loop. The optical self-injection locked loop adjusts the resonance quality factor of the resonant cavity of the laser. It is used to improve and narrow the linewidth of lasers, and provides ultrastable cavity phase locking. The loop is an optical self-injection locked loop, which is used to stabilize the phase of an optical signal and feeds Back-controlling the laser current further reduces the laser frequency noise and optical self-injection. The lock loop is combined with an ultra-stable cavity phase-lock loop to achieve high stability of the oscillation frequency. Realizes ultra-narrow linewidth laser output.

[0006] The optical self-injection locked loop comprises a laser and an optical fiber circulator. , two 1×2 optical fiber couplers, one phase modulator, and one ultra-stable optical resonator cavity. , one polarization controller, one erbium doped fiber amplifier, one optical bandpass The ultra-stable cavity phase locus consists of a filter, a piezoelectric ceramic controller, The loop consists of one laser, one optical fiber circulator, and two 1x2 optical fibers. A fiber optic coupler, a phase modulator, a superstable optical resonant cavity, and an avalanche a photodiode, an electrical bandpass filter, an analog signal source, A power distributor, a mixer, a loop filter, an amplifier, a servo circuit, The system consists of two adder circuits and one constant current source, and is based on an optical self-injection locked loop and an ultrastable cavity phase shifter. A phase-locked loop is a system that has common components, one laser, one optical fiber circuit, and modulator, two 1×2 fiber optic couplers, one phase modulator, and one optical resonator cavity. Includes tea.

[0007] Furthermore, the optical self-injection locked loop comprises: a laser for generating an optical signal L1 at a second port of the optical fiber circulator; One-way transmission of optical signal L1 from the second port to the third port of the optical fiber circulator An optical fiber circulator for realizing transmission, wherein the output optical signal of the third port is L2 1, an optical fiber coupler 1×2 is connected to the optical fiber coupler 2, and the optical signal L2 is transmitted to the optical fiber coupler 2. With the curator, a first 1×2 optical fiber coupler for splitting the optical signal L2 into two optical signals L31 and L32; an optical signal L31 is transmitted to a phase modulator and an optical signal L32 is output by said device; a first 1×2 optical fiber coupler, the first 1×2 optical fiber coupler being a narrow linewidth laser signal; The electrical signal E22 is modulated onto the optical signal L31 to generate the optical signal L4, and an optical resonator is provided. a phase modulator for transmitting the phase signal to the bitness; an optical resonant cavity, wherein the optical signal L4 is a Different phase changes occur in the two sidebands of the signal L4, and at this time the optical signal is recorded as L5. and the optical signal L5 is transmitted to a second 1×2 optical fiber coupler. and, A second 1 × 2 optical fiber coupler for splitting the optical signal L5 into two optical signals L61 and L62. The optical signal L61 is transmitted to an erbium doped optical fiber amplifier, and the optical signal L62 is transmitted to an erbium doped optical fiber amplifier. a second 1×2 optical fiber coupler through which the avalanche photodiode is coupled; An erbium-doped optical fiber amplifier for amplifying the optical signal L61 to the optical signal L7. an erbium-doped optical fiber amplifier in which the optical signal L7 is transmitted to an optical bandpass filter; The spontaneous emission noise introduced by the erbium-doped fiber amplifier in the optical signal L7 is an optical bandpass filter for reducing the polarization of the optical signal L8 and outputting the optical signal L8 to the polarization controller; , Adjust the polarization state of the optical self-injection locked loop, and after the optical signal L8 passes through the polarization controller a polarization controller for outputting an optical signal L9 to the piezoelectric ceramic controller; Controlled by electrical signal E7, it allows fine adjustment to the length of the optical self-injection locked loop. and a pressure for outputting the optical signal L10 to a first port of the optical fiber circulator. an electro-ceramic controller; The optical signal L10 enters a first port of the optical fiber circulator and is output in one direction to a second port. port, which then injects the light into the laser to complete the optical self-injection locked loop. Forming The ultrastable cavity phase-locked loop comprises: a laser for generating an optical signal L1 at a second port of the optical fiber circulator; One-way transmission of optical signal L1 from the second port to the third port of the optical fiber circulator An optical fiber circulator for realizing transmission, wherein the output optical signal of the third port is L2 1, an optical fiber coupler 1×2 is connected to the optical fiber coupler 2, and the optical signal L2 is transmitted to the optical fiber coupler 2. With the curator, a first 1×2 optical fiber coupler for splitting the optical signal L2 into two optical signals L31 and L32; an optical signal L31 is transmitted to a phase modulator and an optical signal L32 is output by said device; a first 1×2 optical fiber coupler, the first 1×2 optical fiber coupler being a narrow linewidth laser signal; The electrical signal E22 is modulated onto the optical signal L31 to generate the optical signal L4, and an optical resonator is provided. a phase modulator for transmitting the phase signal to the bitness; an optical resonant cavity, wherein the optical signal L4 is a Different phase changes occur in the two sidebands of the signal L4, and at this time the optical signal is recorded as L5. and the optical signal L5 is transmitted to a second 1×2 optical fiber coupler. and, A second 1 × 2 optical fiber coupler for splitting the optical signal L5 into two optical signals L61 and L62. The optical signal L61 is transmitted to an erbium doped optical fiber amplifier, and the optical signal L62 is transmitted to an erbium doped optical fiber amplifier. a second 1×2 optical fiber coupler through which the avalanche photodiode is coupled; for converting the optical signal L62 into an electrical signal E1 and transmitting it to an electrical bandpass filter; an avalanche photodiode; Filter the electrical signal E1 and output the electrical signal E2 to the radio frequency port of the mixer. an electrical bandpass filter; an analog signal source for generating a reference electrical signal E3, an analog signal source, the analog signal being transmitted to a power splitter; Divide the electrical signal E3 into electrical signals E41 and E42 that have the same power and a phase difference of 90°. The electric signal E42 is transmitted to a phase modulator, and the electric signal E41 is transmitted to a mixer. a power divider connected to a local oscillation port of the The phase difference between the electrical signal E41 and the electrical signal E2 is compared to obtain an electrical signal E5, and the loop-f a mixer for transmitting the signal to the filter; A loop that performs integration and other processing on electrical signal E5 to generate electrical signals E61 and E62. A loop filter in which an electric signal E61 is transmitted to an amplifier and an electric signal E62 is transmitted to a servo circuit. a loop filter provided to the path; The control signal E61 is amplified to generate an electrical signal E7 to control the piezoelectric ceramic controller. an amplifier for controlling the a servo circuit that converts the electric signal E62 into a current signal E8 and transmits it to an adder circuit; The current signal E8 is added to the current signal E9 output by the constant current source, and feedback control is performed. and a summing circuit for obtaining a current E10 of the control laser; The electrical signal E7 controls the piezoelectric ceramic controller to form an optical self-injection lock loop optical signal. The electrical signal E10 is used to control the phase of the feedback control laser. The current is used to reduce the phase noise of the laser, and both are ultra-stable capacitances. The closed-loop control of the bitness phase-locked loop is realized. Effect of the Invention

[0008] The apparatus of the present invention includes an optical self-injection locked loop and an ultrastable cavity phase locked loop. In addition, the optical self-injection locked loop can improve the quality factor of the laser resonant cavity and reduce the linewidth. The narrow-width, ultrastable cavity phase-locked loop is a novel technique for optimizing the loop length and laser power of optical self-injection locking. By adjusting the driving current of the laser, the frequency of the laser is synchronized with the optical resonant cavity. This further reduces the frequency noise of the laser and improves the linewidth narrowing rate of the laser. The ultra-stable cavity phase-locked loop provides stable frequency control of the laser. Due to precise control, the occurrence of mode hopping caused by the drift of the laser frequency is avoided. , and improves the stability of the system. To provide a stable narrow linewidth laser source for radar, industrial device processing, medical applications, etc. can be done. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram of a specific structure of the device of the present invention; [Diagram 2] FIG. 2 is a block diagram of an s-domain model of the device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In order to more specifically describe the present invention, the following drawings and detailed description are provided. The technical solution of the present invention will be described in detail in conjunction with the above.

[0011] As shown in FIG. 1, the optical self-injection locked loop includes a laser 1, an optical fiber circulator 2, and a a phase modulator 2, a first 1×2 optical fiber coupler 3, a phase modulator 4, an optical resonant cavity 5, A second 1×2 optical fiber coupler 6, an erbium doped optical fiber amplifier 7, an optical bandpass filter The optical filter 8, the polarization controller 9, and the piezoelectric ceramic controller 10 are arranged between them. Both are connected via optical fiber, and the light output from the laser is optical self-injection. After passing through the locking loop, it returns to the inside of the laser, which is the loop of the resonant cavity of the laser. This corresponds to increasing the loop length, which further improves the quality factor of the laser device, thereby This reduces the linewidth of the laser, but the adjacent modes are lost due to the effect of increasing the loop length and gain competition. It is possible that the oscillation conditions are satisfied and that hopping may occur in the oscillation mode. To induce this, an optical resonant cavity is added inside the loop to filter out the desired mode. The ultra-stable cavity phase locking filter can improve system stability. The group is configured as follows: laser 1, optical fiber circulator 2, first 1×2 optical A fiber coupler 3, a phase modulator 4, an optical resonant cavity 5, a second 1×2 optical fiber coupler The avalanche photodiode 11 and the sensor 6 are connected via optical fiber. , an electrical bandpass filter 12, an analog signal source 14, a power splitter 15, and a mixer 13. are connected via a coaxial cable, and include a loop filter 16, an amplifier 17, and a servo The circuit 18, the summing circuit 19, and the constant current source 20 are connected via copper conductors.

[0012] The specific operation method is as follows: First, the frequency of the laser is adjusted to the ultra-stable optical cavity. The ultrastable cavity phase-locked loop is tuned to the resonant frequency of the cavity and the periphery of the laser. The wavenumber offset optical resonant cavity converts the information into a voltage signal, and the laser emits light. After being locked by self-injection, the laser frequency increases with increasing loop length. Since the vibration condition is determined by the loop length, the vibration can be adjusted by fine-tuning the loop length. The frequency of the laser can be synchronized with the optical resonant cavity, and the loop jitter can be eliminated. The high frequency components of the control signal are also suppressed by reducing the frequency noise of the laser. It is used to control the drive current and is used to reduce frequency noise caused by current noise. The frequency noise of the laser can be further suppressed, i.e., the linewidth of the laser can be further narrowed. will be done.

[0013] In this embodiment, the s-domain model is shown in FIG. 2. As can be seen from the figure, the ultra-stable cavity In the absence of phase-locked loop control, the input noise is Therefore, the gain of noise suppression is K SIL And K S IL is much smaller than 1, which indicates the suppression of frequency noise in optical self-injection locking. After adding an ultra-stable cavity phase-locked loop for feedback control, the closed-loop The frequency noise suppression gain of the system is derived as follows:

[0014] [formula] JPEG2025010112000002.jpg20132 where, JPEG2025010112000003.jpg1010 represents the output frequency noise of a laser device. JPEG2025010112000004.jpg1011 represents the input frequency noise of the laser. JPEG2025010112000005.jpg1120 represents the frequency discrimination gain of the ultra-stable cavity phase-locked loop, JPEG2025010112000006.jpg1114 represents the transfer function of the loop filter, JPEG2025010112000007.jpg1116 represents the frequency modulation response of the laser current; JPEG2025010112000008.jpg1116 represents the frequency response of the piezoelectric ceramic controller, JPEG2025010112000009.jpg1117 represents the response of the laser frequency to the loop length in optical self-injection locking. As a result, compared to a single optical self-injection locking system, the structure according to the present invention has a low optical phase noise. Suppression ratio It becomes clear that JPEG2025010112000010.jpg can be improved by 11107 times.

[0015] The above description of the embodiments is intended to enable those skilled in the art to easily understand and apply the present invention. Various modifications can be easily made to the above embodiment without any creative effort. Those skilled in the art will appreciate that the general principles described herein can be applied to other embodiments. Therefore, the present application is not limited to the above embodiment, and the disclosure of the present invention is not intended to be limiting to the present invention. Therefore, any improvements and modifications made to the present invention should fall within the protection scope of the present invention. be. [Explanation of symbols]

[0016] 1—laser, 2—optical fiber circulator, 3—first 1×2 Optical coupler, 4—phase modulator, 5—optical resonant cavity, 6—second 1× 2—optical coupler, 7—erbium-doped optical fiber amplifier, 8—optical bandpass filter 9—Polarization controller; 10—Piezoelectric ceramic controller; 11— ;Avalanche photodiode, 12—Electrical bandpass filter, 13—Microsecond 14—analog signal source; 15—power divider; 16—loop filter 17—electrical amplifier, 18—servo circuit, 19—adding circuit, 20 2; Constant current source.

Claims

1. Ultra-narrow linewidth laser generator using an optical self-injection locked loop and an ultra-stable cavity phase lock loop and an optical self-injection locked loop, the optical self-injection locked loop being adapted to adjust the resonant quality of the resonant cavity of the laser. It is used to improve the factor and narrow the linewidth of the laser, and produces an ultrastable cavity phase The lock loop is an optical self-injection locked loop, which is used to stabilize the phase of the optical signal. Feedback control of the laser current further reduces the laser frequency noise and provides automatic light control. High frequency stability achieved by combining a self-injection locked loop and an ultra-stable cavity phase locked loop This is an ultra-narrow linewidth laser generator that realizes ultra-narrow linewidth laser output.

2. The optical self-injection locked loop comprises: a laser for generating an optical signal L1 at a second port of the optical fiber circulator; The optical signal L1 is unidirectional from the second port to the third port of the optical fiber circulator. An optical fiber circulator for realizing transmission, wherein the output optical signal of the third port is L2 The optical fiber coupler 1x2 transmits the optical signal L2 to the first optical fiber coupler 1x2. With the curator, a first 1×2 optical fiber coupler for splitting the optical signal L2 into two optical signals L31 and L32; an optical signal L31 is transmitted to a phase modulator and an optical signal L32 is output by the device; a first 1×2 optical fiber coupler, the first 1×2 optical fiber coupler being a narrow linewidth laser signal; The electrical signal E22 is modulated onto the optical signal L31 to generate the optical signal L4, and an optical resonator is provided. a phase modulator for transmitting the phase signal to the bitness; an optical resonant cavity, wherein the optical signal L4 is a At this time, different phase changes occur in the two sidebands of the optical signal L4, and the optical signal is recorded as L5. and the optical signal L5 is transmitted to a second 1×2 optical fiber coupler. and, a second 1×2 optical fiber coupler for splitting the optical signal L5 into two optical signals L61 and L62; The optical signal L61 is transmitted to an erbium doped optical fiber amplifier, and the optical signal L62 is transmitted to an erbium doped optical fiber amplifier. a second 1×2 optical fiber coupler through which the avalanche photodiode is coupled; An erbium-doped optical fiber amplifier for amplifying the optical signal L61 to the optical signal L7. an erbium doped optical fiber amplifier in which the optical signal L7 is transmitted to an optical bandpass filter; The spontaneous emission noise introduced by the erbium doped optical fiber amplifier in the optical signal L7 is expressed as an optical bandpass filter for reducing the polarization of the optical signal L8 and outputting the optical signal L8 to the polarization controller; 、 The polarization state of the optical self-injection locked loop is adjusted, and the optical signal L8 passes through the polarization controller. a polarization controller for outputting an optical signal L9 to the piezoelectric ceramic controller; Controlled by electrical signal E7, it allows fine adjustment to the length of the optical self-injection locked loop. and a pressure for outputting the optical signal L10 to a first port of the optical fiber circulator. an electro-ceramic controller; The optical signal L10 enters a first port of the optical fiber circulator and is output in one direction to a second port. port, which then injects the light into the laser to complete the optical self-injection locked loop. The generator of claim 1, further comprising:

3. The ultrastable cavity phase-locked loop comprises: a laser for generating an optical signal L1 at a second port of the optical fiber circulator; The optical signal L1 is unidirectional from the second port to the third port of the optical fiber circulator. An optical fiber circulator for realizing transmission, wherein the output optical signal of the third port is L2 The optical fiber coupler 1x2 transmits the optical signal L2 to the first optical fiber coupler 1x2. With the curator, a first 1×2 optical fiber coupler for splitting the optical signal L2 into two optical signals L31 and L32; an optical signal L31 is transmitted to a phase modulator and an optical signal L32 is output by the device; a first 1×2 optical fiber coupler, the first 1×2 optical fiber coupler being a narrow linewidth laser signal; The electrical signal E22 is modulated onto the optical signal L31 to generate the optical signal L4, and an optical resonator is provided. a phase modulator for transmitting the phase signal to the bitness; an optical resonant cavity, wherein the optical signal L4 is a At this time, different phase changes occur in the two sidebands of the optical signal L4, and the optical signal is recorded as L5. and the optical signal L5 is transmitted to a second 1×2 optical fiber coupler. and, a second 1×2 optical fiber coupler for splitting the optical signal L5 into two optical signals L61 and L62; The optical signal L61 is transmitted to an erbium doped optical fiber amplifier, and the optical signal L62 is transmitted to an erbium doped optical fiber amplifier. a second 1×2 optical fiber coupler through which the avalanche photodiode is coupled; for converting the optical signal L62 into an electrical signal E1 and transmitting it to an electrical bandpass filter; an avalanche photodiode; The electrical signal E1 is filtered and the electrical signal E2 is output to the radio frequency port of the mixer. an electrical bandpass filter; an analog signal source for generating a reference electrical signal E3, an analog signal source, the analog signal being transmitted to a power splitter; The electrical signal E3 is divided into electrical signals E41 and E42 having equal power and a phase difference of 90°. The power splitter is configured such that an electric signal E42 is transmitted to a phase modulator and an electric signal E41 is transmitted to a mixer. a power divider connected to a local oscillation port of the The phase difference between the electrical signal E41 and the electrical signal E2 is compared to obtain an electrical signal E5, and the loop-f a mixer for transmitting the signal to the filter; A loop that performs integration and other processes on the electrical signal E5 to generate electrical signals E61 and E62. The loop filter is a loop filter in which an electric signal E61 is transmitted to an amplifier and an electric signal E62 is transmitted to a servo circuit. a loop filter provided to the path; The control signal E61 is amplified to generate an electrical signal E7 to control the piezoelectric ceramic controller. an amplifier for controlling the a servo circuit that converts the electric signal E62 into a current signal E8 and transmits it to an adder circuit; The current signal E8 is added to the current signal E9 output by the constant current source, and feedback control is performed. and a summing circuit for obtaining a current E10 of the control laser; The electrical signal E7 controls the piezoelectric ceramic controller to form an optical self-injection locked loop optical signal. The electrical signal E10 is used to control the phase of the feedback control laser. The current is used to reduce the phase noise of the laser, and both are ultra-stable capacitances.

2. The method according to claim 1, further comprising the step of: Generator.

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