Optical frequency comb and trace gas detection apparatus and method thereof

Abstract

This invention discloses an optical frequency comb and its trace gas detection device and method, relating to the fields of laser technology and trace gas detection technology. The optical frequency comb consists of a first tunable laser (1) and a second tunable laser (2) connected to a 2×1 optical coupler (3), the 2×1 optical coupler (3), a Mach-Zehnder modulator (4), and a spectrometer (6) connected in sequence; a tunable DC power supply (10) 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) connected to a three-in-one coupler (5); and the three-in-one coupler (5) connected to the Mach-Zehnder modulator (4). This optical frequency comb, using only a single Mach-Zehnder modulator, has advantages such as tunable optical frequency comb spectral lines, a large number of spectral lines, and a wide bandwidth, making it better suited for applications in laser and trace gas detection fields.

Description

Technical Field

[0001] This invention relates to the fields of laser technology and trace gas detection technology, and in particular to an optical frequency comb and its trace gas detection device and method. Background Technology

[0002] An optical frequency comb, also known as an optical frequency comb, is an optical spectrum resembling "comb teeth," composed of multiple discrete, equally spaced, and equal-amplitude frequency components. It acts like a precise "optical ruler," allowing for accurate calibration and measurement of optical frequencies. With the development of its technology, optical frequency comb technology has also expanded into fields such as precision measurement, quantum communication, and optical communication. Current methods for generating optical frequency combs mainly include: mode-locked laser method, Kerr microcavity method, and electro-optic modulation method. Among these, the electro-optic modulation method has received widespread attention and research due to its simple structure, adjustable repetition frequency, and high comb tooth power.

[0003] Common electro-optic modulation methods for generating optical frequency combs utilize external modulators, including but not limited to intensity modulators, phase modulators, and electroabsorbers. Current commonly used generation devices are generally based on cascades or combinations of these modulators; however, the bandwidth of the generated optical frequency comb is typically limited due to the inherent bandwidth constraints of the modulators themselves. Furthermore, the gas detection field requires wideband measurements of gas molecules, making this method unsuitable for trace gas detection. Summary of the Invention

[0004] The purpose of this invention is to address the problems and shortcomings of existing technologies by providing an optical frequency comb and its trace gas detection device and method. The optical frequency comb proposed in this invention has advantages such as simple structure, topological flexibility, tunable spectral lines, a large number of spectral lines, and wide bandwidth, making it well-suited for application in the field of trace gas detection.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] I. Optical Frequency Comb

[0007] This 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 DC power supply.

[0008] The connection relationship is:

[0009] The first tunable laser and the second tunable laser are respectively connected to a 2×1 optical coupler. 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 RF signal generator, the second RF signal generator, and the third RF signal generator are respectively connected to a three-in-one coupler. The three-in-one coupler is connected to the Mach-Zehnder modulator.

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

[0011] Furthermore, the signals generated by the three radio frequency signal generators are sine wave signals that satisfy the multiple.

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

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

[0014]

[0015] Where 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 signal generated by the three RF signal generators after passing through a three-in-one coupler is as follows:

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

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

[0019] The expression for the output optical signal after continuous light passes through the Mach-Zehnder modulator is:

[0020]

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

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

[0023] II. Trace Gas Detection Device

[0024] It includes an optical frequency comb, an optical amplifier, a highly nonlinear optical fiber, a gas detection unit, and a data acquisition unit connected in sequence.

[0025] III. Trace Gas Detection Methods

[0026] ① Generate an optical frequency comb;

[0027] ② By passing the optical frequency comb through an optical amplifier and a highly nonlinear optical fiber, a wider and flatter optical frequency comb can be obtained;

[0028] ③ Input to the gas detection unit;

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

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

[0031] ①This optical frequency comb has the advantages of adjustable optical frequency comb spectral lines, a large number of spectral lines, and wide bandwidth when using only a single Mach-Zehnder modulator, which makes it better suited for laser and trace gas detection.

[0032] ②This trace gas detection device can meet the requirements of broadband detection of gas molecules, making it a promising application. Attached Figure Description

[0033] Figure 1 This is a block diagram of the structure of this 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—First radio frequency signal generator;

[0041] 8—Second radio frequency signal generator;

[0042] 9—Third radio frequency signal generator;

[0043] 10—Tuned DC power supply.

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

[0045] Figure 3 This is a structural block diagram of the trace gas detection device. (See diagram:)

[0046] A—Optical frequency comb;

[0047] B—Optical amplifier;

[0048] C—Highly nonlinear optical fiber;

[0049] D—Gas detection unit;

[0050] E—Data Acquisition Unit. Detailed Implementation

[0051] The following detailed description is provided in conjunction with the accompanying drawings and specific embodiments.

[0052] I. Optical Frequency Comb

[0053] 1. Overall

[0054] like Figure 1 This 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. 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 radio frequency signal generator 7, the second radio frequency signal generator 8, and the third radio frequency 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 path through a 2×1 optical coupler 3, and then connected to the optical input end of the Mach-Zehnder modulator 4.

[0058] The first radio frequency signal generator 7, the second radio frequency signal generator 8, and the third radio frequency signal generator 9 are combined into one radio frequency signal through the three-in-one coupler 5 and input to the radio frequency signal input terminal 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 terminal of the Mach-Zehnder modulator 4 is connected to the optical input terminal of the spectrometer 6;

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

[0062] 2. Functional components

[0063] 01) First tunable laser 1

[0064] The first tunable laser 1 is an ultraviolet, visible, infrared, or terahertz light source with a tunable center wavelength, outputting continuous wave laser light.

[0065] 02) Second tunable laser 2

[0066] The second tunable laser 2 is an ultraviolet, visible, infrared, or terahertz light source with a tunable center wavelength, outputting continuous wave laser light.

[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 that 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 radio frequency drive signals into the same channel.

[0073] 06) Spectrometer 6

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

[0075] 07) 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, which outputs a sine wave radio frequency signal with adjustable frequency.

[0077] 08) Second radio frequency signal generator 8

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

[0079] 09) Third radio frequency signal generator 9

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

[0081] 10) Adjustable DC power supply

[0082] The tunable DC power supply 10 is a DC power supply that provides an adjustable voltage to provide 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, with an optical power of 0 dBm; the radio frequency signals of the first radio frequency signal generator 7, the second radio frequency signal generator 8, and the third radio frequency signal generator 9 are set to 20 GHz, 40 GHz, and 60 GHz, respectively, which can generate a flat frequency comb with 19 comb lines, a comb tooth spacing of 20 GHz, and a flatness of 0.66 dB. Figure 2 As shown.

[0084] 3. Working Mechanism

[0085] The two continuous-wave laser beams output from the first tunable laser 1 and the second tunable laser 2 are coupled into a single input via a 2×1 optical coupler 3 and then the continuous-wave laser is intensity modulated, converting the single-wavelength continuous-wave laser into a series of optical frequency combs with the same spacing.

[0086] II. 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 Units

[0090] 01) Optical Frequency Comb A

[0091] As mentioned above.

[0092] 02) Optical Amplifier B

[0093] Optical amplifier B is a device that amplifies the power of an input optical signal based on a fabrication pattern, and amplifies the power of an intensity-modulated optical signal.

[0094] 03) Highly nonlinear optical fiber C

[0095] Highly nonlinear fiber C is a type of optical fiber with a very high nonlinear coefficient, which broadens the spectrum of the optical signal at the input end.

[0096] 04) Gas detection unit D

[0097] The gas detection unit D is a long-path gas absorption cell, photothermal gas reaction cell, or photoacoustic gas reaction cell, serving as a reaction unit between light and gas.

[0098] 05) Data Acquisition Unit E

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

[0100] 3) Working mechanism

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

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optical frequency comb, characterized in that: It 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). The connection relationship is: The first tunable laser (1) and the second tunable laser (2) are respectively connected to the 2×1 optical coupler (3), 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 radio frequency signal generator (7), the second radio frequency signal generator (8) and the third radio frequency 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); The two tunable lasers have similar but different center wavelengths; The signals generated by the three radio frequency signal generators are sine wave signals that meet the multiple requirements; The three-in-one coupler superimposes the sinusoidal signals generated by the three radio frequency signal generators to form a modulated signal; In the optical frequency comb, the signal after the two tunable lasers are coupled through a 2×1 optical coupler is: Where E0 represents the light intensity output by the tunable laser, and ω1 and ω2 are the angular frequencies of the two tunable lasers; The signal generated by the three RF signal generators after passing through a three-in-one coupler is as follows: s(t)=sin(2πf1t+θ1)+sin(2πf2t+θ2)+sin(2πf3t+θ3) Where f1, f2, and f3 are the center frequencies of the three signal generators, and θ1, θ2, and θ3 are the initial phases of the three signal generators; The expression for the output optical signal after continuous light passes through the Mach-Zehnder modulator is: in, φ is the modulation coefficient. i For phase change, V π J is the half-wave voltage of the modulator. n It is a Bessel function of the first kind, order n; According to the above expression, by reasonably adjusting the modulation coefficient, the amplitude of each sideband can be greatly affected, thereby obtaining a high-quality optical frequency comb.

2. The trace gas detection device based on the optical frequency comb of 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) connected in sequence; The trace gas detection method of the trace gas detection device is as follows: ① Generate an optical frequency comb; ② By passing the optical frequency comb through an optical amplifier and a highly nonlinear optical fiber, a wider and flatter optical frequency comb can be obtained; ③ Input to the gas detection unit; ④ The data acquisition unit acquires the output signal of the gas detection unit to obtain spectral information.

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