Optical frequency comb and trace gas detection device and method thereof

Abstract

The invention discloses an optical frequency comb and a trace gas detection device and method thereof, and relates to the technical field of laser technology and trace gas detection. The optical frequency comb is characterized in that a first tunable laser (1) and a second tunable laser (2) are respectively connected with a 2 * 1 optical coupler (3), and the 2 * 1 optical coupler (3), a Mach-Zehnder modulator (4) and a spectrograph (6) are sequentially connected; the tunable direct-current power supply (10) is connected with the Mach-Zehnder modulator (4); the first radio frequency signal generator (7), the second radio frequency signal generator (8) and the third radio frequency signal generator (9) are respectively connected with the three-in-one coupler (5); and the three-in-one coupler (5) is connected with the Mach-Zehnder modulator (4). The optical frequency comb has the advantages of being adjustable in spectral line, large in number of spectral lines, wide in frequency band and the like under the condition that only a single Mach-Zehnder modulator is used, so that the optical frequency comb can be better applied to the field of laser and trace gas detection.

Description

Technical Field

[0001] The present invention relates to the field of laser technology and trace gas detection technology, and in particular to an optical frequency comb and a trace gas detection device and method thereof. Background Art

[0002] An optical frequency comb, also known as a light comb, is an optical spectrum shaped like "comb teeth" composed of multiple discrete, equally spaced frequency components of equal amplitude. It is like an accurate "light ruler" that can accurately calibrate and measure optical frequencies. With the development of its technology, optical frequency comb technology has also continued to develop into fields such as precision measurement, quantum communication, and optical communication. The current methods for generating optical frequency combs mainly include: mode-locked laser method, Kerr microcavity method, and electro-optical modulation method. Among them, the electro-optical modulation method has received widespread attention and research due to its simple structure, adjustable repetition frequency, and high comb power.

[0003] The common electro-optical modulation method for generating optical frequency combs is to use external modulators, including but not limited to intensity modulators, phase modulators, and electro-absorbers. Currently, the commonly used generation devices are generally based on the cascade or combination of the above modulators. However, due to the limitation of the modulator's own bandwidth, the bandwidth of the generated optical frequency comb is usually small. In the field of gas detection, it is necessary to measure the gas molecules with a wide bandwidth, so it is difficult to act in the field of trace gas detection. Summary of the invention

[0004] The purpose of the present invention is to solve the problems and shortcomings of the prior art and provide an optical frequency comb and a trace gas detection device and method thereof. The optical frequency comb proposed in the present invention has the advantages of simple structure, topology, adjustable optical frequency comb spectral lines, a large number of spectral lines and wide frequency band, so that it can be well applied in the field of trace gas detection.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] 1. Optical frequency comb

[0007] The optical frequency comb includes a first tunable laser, a second tunable laser, a 2×1 optical coupler, a Mach-Zehnder modulator, a three-in-one coupler, a spectrometer, a first radio frequency signal generator, a second radio frequency signal generator, a third radio frequency signal generator and a tunable direct current power supply;

[0008] The connection relationship is:

[0009] The first tunable laser and the second tunable laser are respectively connected to the 2×1 optical coupler, and the 2×1 optical coupler, the Mach-Zehnder modulator and the spectrometer are connected in sequence; the tunable DC power supply 1 is connected to the Mach-Zehnder modulator; the first radio frequency signal generator, the second radio frequency signal generator and the third radio frequency signal generator are respectively connected to the three-in-one coupler; the three-in-one coupler is connected to the Mach-Zehnder modulator.

[0010] Furthermore, the central wavelengths of the two tunable lasers are similar but different.

[0011] Furthermore, the signals generated by the three radio frequency signal generators are sinusoidal wave signals that meet the multiples.

[0012] Furthermore, the three-in-one coupler superimposes the sinusoidal wave signals generated by the three radio frequency signal generators to form a modulated signal.

[0013] Furthermore, in the optical frequency comb, the signal of two tunable lasers coupled by a 2×1 optical coupler is:

[0014]

[0015] Wherein, E0 represents the light intensity output by the tunable laser, and ω1 and ω2 are the angular frequencies of the two tunable lasers.

[0016] The signals of the three RF signal generators after passing through a three-in-one coupler are:

[0017] s(t)=sin(2πf1t+θ1)+sin(2πf2t+θ2)+sin(2πf3t+θ3)

[0018] Among them, f1, f2, f3 are the center frequencies of the three signal generators respectively, and θ1, θ2, θ3 are the initial phases of the three signal generators respectively.

[0019] When continuous light passes through the Mach-Zehnder modulator, the output optical signal expression is:

[0020]

[0021] in, is the modulation coefficient, φ i is the phase change, V π is the half-wave voltage of the modulator, J n is the nth-order Bessel function of the first kind.

[0022] According to the above expression, the amplitude of each order sideband can be greatly affected by properly adjusting the modulation coefficient, thereby obtaining a high-quality optical frequency comb.

[0023] 2. Trace Gas Detection Device

[0024] The invention comprises an optical frequency comb, an optical amplifier, a highly nonlinear optical fiber, a gas detection unit and a data acquisition unit which are connected in sequence.

[0025] 3. Trace Gas Detection Methods

[0026] ①Generate optical frequency comb;

[0027] ② Pass the optical frequency comb through an optical amplifier and a highly nonlinear optical fiber to obtain a wider and flatter optical frequency comb;

[0028] ③Input to the gas detection unit;

[0029] ④The data acquisition unit collects the output signal of the gas detection unit to obtain spectral information.

[0030] The present invention has the following advantages and positive effects:

[0031] ① This optical frequency comb has the advantages of adjustable optical frequency comb spectral lines, a large number of spectral lines, and wide frequency band when only a single Mach-Zehnder modulator is used, so it can be better applied in the field of laser and trace gas detection;

[0032] ② This trace gas detection device can meet the requirements of wide-band detection of gas molecules, giving it a good application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the block diagram of the structure of the optical frequency comb.

[0034] 1—first tunable laser;

[0035] 2—second tunable laser;

[0036] 3—2×1 optical coupler;

[0037] 4—Mach-Zehnder modulator;

[0038] 5—three-in-one coupler;

[0039] 6—Spectrometer;

[0040] 7—a first radio frequency signal generator;

[0041] 8—a second radio frequency signal generator;

[0042] 9—third radio frequency signal generator;

[0043] 10—Tunable DC power supply.

[0044] Figure 2It is a 19-line flat optical frequency comb diagram of the optical frequency comb.

[0045] Figure 3 This is a structural block diagram of the trace gas detection device, in which:

[0046] A—Optical frequency comb;

[0047] B—optical amplifier;

[0048] C—high nonlinear optical fiber;

[0049] D—gas detection unit;

[0050] E—Data acquisition unit. DETAILED DESCRIPTION

[0051] The following is a detailed description with reference to the accompanying drawings and specific embodiments.

[0052] 1. Optical frequency comb

[0053] 1. Overall

[0054] like Figure 1 The optical frequency comb includes a first tunable laser 1, a second tunable laser 2, a 2×1 optical coupler 3, a Mach-Zehnder modulator 4, a three-in-one coupler 5, a spectrometer 6, a first radio frequency signal generator 7, a second radio frequency signal generator 8, a third radio frequency signal generator 9 and a tunable DC power supply 10;

[0055] The connection relationship is:

[0056] The first tunable laser 1 and the second tunable laser 2 are respectively connected to the 2×1 optical coupler 3, and the 2×1 optical coupler 3, the Mach-Zehnder modulator 4 and the spectrometer 6 are connected in sequence; the tunable DC power supply 10 is connected to the Mach-Zehnder modulator 4; the first RF signal generator 7, the second RF signal generator 8 and the third RF signal generator 9 are respectively connected to the three-in-one coupler 5; the three-in-one coupler 5 is connected to the Mach-Zehnder modulator 4.

[0057] The first tunable laser 1 and the second tunable laser 2 are combined into one channel through a 2×1 optical coupler 3, and then connected to the optical input end of a Mach-Zehnder modulator 4;

[0058] The first RF signal generator 7, the second RF signal generator 8 and the third RF signal generator 9 are combined into one RF signal through the three-in-one coupler 5 and input to the RF signal input end of the Mach-Zehnder modulator 4;

[0059] The tunable DC power supply 10 is connected to the DC input terminal of the Mach-Zehnder modulator 4;

[0060] The optical output end of the Mach-Zehnder modulator 4 is connected to the optical input end of the spectrometer 6;

[0061] The Mach-Zehnder modulator 4 modulates the intensity of the input laser light.

[0062] 2. Functional components

[0063] 01) The first tunable laser 1

[0064] The first tunable laser 1 is an ultraviolet, visible, infrared light source or a terahertz light source with an adjustable central wavelength, and outputs continuous wave laser

[0065] 02) Second tunable laser 2

[0066] The second tunable laser 2 is an ultraviolet, visible, infrared light source or a terahertz light source with an adjustable central wavelength, and outputs continuous wave laser

[0067] 03)2×1 Optocoupler 3

[0068] The 2×1 optical coupler 3 is an optical coupling device that couples two laser beams into the same path.

[0069] 04) Mach-Zehnder Modulator 4

[0070] The Mach-Zehnder modulator 4 is an electro-optic intensity modulator or a dual parallel Mach-Zehnder modulator, which modulates the input laser

[0071] 05) Three-in-one coupler 5

[0072] The three-in-one coupler 5 is an electrical coupling device that couples three RF drive signals into one channel.

[0073] 06) Spectrometer 6

[0074] Spectrometer 6 is an optical device used to detect the wavelength and power information of optical signals.

[0075] 07) The first radio frequency signal generator 7

[0076] The first radio frequency signal generator 7 is a sine wave signal generator or an arbitrary waveform signal generator, and outputs a frequency-adjustable sine wave radio frequency signal.

[0077] 08) Second RF signal generator 8

[0078] The second RF signal generator 8 is a sine wave signal generator or an arbitrary waveform signal generator, and outputs a sine wave RF signal with adjustable frequency.

[0079] 09) The third radio frequency signal generator 9

[0080] The third RF signal generator 9 is a sine wave signal generator or an arbitrary waveform signal generator, and outputs a sine wave RF signal with adjustable frequency.

[0081] 10) Tunable DC power supply 10

[0082] The tunable DC power supply 10 is a DC power supply with adjustable voltage, and provides a bias voltage for the Mach-Zehnder modulator 4 .

[0083] In this embodiment, the center wavelengths of the first tunable laser 1 and the second tunable laser 2 are set to 193.1 THz and 193.2 THz respectively, and the optical power is 0 dBm; the RF signal frequencies of the first RF signal generator 7, the second RF signal generator 8 and the third RF signal generator 9 are set to 20 GHz, 40 GHz and 60 GHz respectively, and a flat frequency comb with 19 comb lines can be generated, the comb tooth spacing is 20 GHz, and the flatness is 0.66 dB. Figure 2 shown.

[0084] 3. Working mechanism

[0085] The two continuous wave lasers output by the first tunable laser 1 and the second tunable laser 2 are coupled into a Mach-Zehnder modulator 4 via a 2×1 optical coupler 3, and then the continuous wave lasers are intensity modulated to modulate the single wavelength continuous wave lasers into a series of optical frequency combs with the same intervals.

[0086] 2. Trace gas detection device based on optical frequency comb

[0087] 1. Overall

[0088] like Figure 3 The device includes an optical frequency comb A, an optical amplifier B, a highly nonlinear optical fiber C, a gas detection unit D and a data acquisition unit E which are connected in sequence.

[0089] 2. Functional Unit

[0090] 01) Optical Frequency Comb A

[0091] As mentioned above.

[0092] 02) Optical Amplifier B

[0093] The optical amplifier B is a device that amplifies the power of an input optical signal according to a preparation mode and amplifies the power of an intensity-modulated optical signal.

[0094] 03) Highly nonlinear optical fiber C

[0095] The high nonlinear optical fiber C is an optical fiber with a very high nonlinear coefficient, which performs spectrum broadening on the optical signal at the input end.

[0096] 04) Gas detection unit D

[0097] The gas detection unit D is a long optical path gas absorption cell, a photothermal gas reaction cell or a photoacoustic gas reaction cell, which serves as a light and gas reaction unit.

[0098] 05) Data Acquisition Unit E

[0099] The data acquisition unit E is a functional unit that performs spectrum and power analysis on the input optical signal.

[0100] 3) Working mechanism

[0101] The optical frequency comb A is used as the seed light source, and then the seed light source is amplified by the optical amplifier B. The amplified optical signal is then nonlinearly broadened using a highly nonlinear optical fiber, thereby generating a wider and flatter optical frequency comb. Figure 3 As shown, it is input into the gas detection unit D as an excitation light source. According to the Beer-Lambert law, the optical frequency comb will change in intensity after gas absorption, and then the absorption spectrum signal is collected by the data acquisition unit E.

[0102] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical frequency comb, characterized in that: The invention comprises a first tunable laser (1), a second tunable laser (2), a 2×1 optical coupler (3), a Mach-Zehnder modulator (4), a three-in-one coupler (5), a spectrometer (6), a first radio frequency signal generator (7), a second radio frequency signal generator (8), a third radio frequency signal generator (9) and a tunable direct current power supply (10); The connection relationship is: The first tunable laser (1) and the second tunable laser (2) are respectively connected to a 2×1 optical coupler (3); the 2×1 optical coupler (3), a Mach-Zehnder modulator (4) and a spectrometer (6) are connected in sequence; a tunable direct current power supply (10) is connected to the Mach-Zehnder modulator (4); a first radio frequency signal generator (7), a second radio frequency signal generator (8) and a third radio frequency signal generator (9) are respectively connected to a three-in-one coupler (5); and the three-in-one coupler (5) is connected to the Mach-Zehnder modulator (4).

2. The trace gas detection device based on the optical frequency comb according to claim 1, characterized in that: It includes an optical frequency comb (A), an optical amplifier (B), a highly nonlinear optical fiber (C), a gas detection unit (D) and a data acquisition unit (E) which are connected in sequence.

3. The trace gas detection method of the trace gas detection device according to claim 1 or 2, characterized in that: ①Generate optical frequency comb; ② Pass the optical frequency comb through an optical amplifier and a highly nonlinear optical fiber to obtain a wider and flatter optical frequency comb; ③Input to the gas detection unit; ④The data acquisition unit collects the output signal of the gas detection unit to obtain spectral information.

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