SYSTEM AND METHOD FOR GENERATING MID-INFRARED OPTICAL FREQUENCY COMB BASED ON LITHIUM NIOBATE MICROCAVITY

Abstract

A system for generating a mid-infrared optical frequency comb based on a lithium niobate microcavity includes pumping units, a beam combining unit, a nonlinear frequency conversion unit and a filtering unit. The pumping units are divided into two paths and are configured to provide two paths of pumping light. The beam combining unit is configured to perform beam combination on the two paths of pumping light The nonlinear frequency conversion unit is configured to receive the beam-combined pumping light and undergo a nonlinear four-wave mixing process to generate a broadband optical frequency comb at a mid-infrared waveband. The filtering unit is configured to filter the remaining pumping light and output a mid-infrared optical frequency comb.

Claims

1. A system for generating a mid-infrared optical frequency comb based on a lithium niobate microcavity, comprising: pumping units, a beam combining unit, a nonlinear frequency conversion unit and a filtering unit; the pumping units being divided into two paths and being configured to provide two paths of pumping light; the beam combining unit being configured to perform beam combination on the two paths of pumping light; the nonlinear frequency conversion unit being configured to receive the beam-combined pumping light and undergo a nonlinear four-wave mixing process to generate a broadband optical frequency comb at a mid-infrared waveband; and the filtering unit being configured to filter the remaining pumping light and output a mid-infrared optical frequency comb.

2. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 1, wherein each pump unit path comprises a narrow linewidth tunable continuous laser source (1), a power amplifier (2) and a polarization controller (4); the narrow linewidth tunable continuous laser source (1) is configured to emit continuous signal light; the power amplifier (2) is configured to amplify the intensity of the signal light; and the polarization controller (4) is configured to adjust the polarization direction of the signal light.

3. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 2, wherein each pump unit path further comprises an attenuator (3) configured to adjust the intensity of the signal light.

4. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 3, wherein the beam combining unit is a beam combiner (5).

5. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 1, wherein the nonlinear frequency conversion unit comprises a lithium niobate microcavity (6) and a temperature controller (7) configured to control the temperature of the lithium niobate microcavity (6).

6. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 5, wherein the filtering unit is a filter (8).

7. A method for generating a mid-infrared optical frequency comb based on the system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 1, comprising the following steps: step 1, adjusting two paths of pumping units to emit two paths of signal light to ensure that intensities and phases of the two paths of signal light meet an intensity condition and a phase matching condition for four-wave mixing; step 2, performing beam combination on the two paths of signal light by a beam combining unit to serve as pumping light of a nonlinear frequency conversion unit; step 3, performing a four-wave mixing effect on an incident pumping light signal by the nonlinear frequency conversion unit to generate a mid-infrared optical frequency comb; and step 4, filtering the remaining pumping light and outputting the mid-infrared optical frequency comb by a filtering unit.

8. The method for generating the mid-infrared optical frequency comb according to claim 7, wherein the incident pumping light signal is subjected to the four-wave mixing effect by virtue of a lithium niobate microcavity (6) in step 3.

9. The method for generating the mid-infrared optical frequency comb according to claim 8, wherein step 1 specifically comprises: step 1.1, adjusting two narrow linewidth tunable continuous laser sources (1) to output two beams of laser, and taking the two beams of laser as the signal light of the pumping units; and step 1.2, adjusting intensities of the two paths of signal light by power amplifiers (2) and attenuators (3) to meet an intensity condition for four-wave mixing; and respectively adjusting polarization directions of the two paths of signal light by two paths of polarization controllers (4) to meet a phase matching condition for four-wave mixing.

10. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 2, wherein the nonlinear frequency conversion unit comprises a lithium niobate microcavity (6) and a temperature controller (7) configured to control the temperature of the lithium niobate microcavity (6).

11. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 3, wherein the nonlinear frequency conversion unit comprises a lithium niobate microcavity (6) and a temperature controller (7) configured to control the temperature of the lithium niobate microcavity (6).

12. The system for generating the mid-infrared optical frequency comb based on the lithium niobate microcavity according to claim 4, wherein the nonlinear frequency conversion unit comprises a lithium niobate microcavity (6) and a temperature controller (7) configured to control the temperature of the lithium niobate microcavity (6).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a schematic frame diagram of the present disclosure;

[0034] FIG. 2 is a schematic structural diagram of a device provided by the present disclosure;

[0035] FIG. 3A is a result diagram of a mid-infrared optical frequency comb under the repetition frequency of 203 GHz;

[0036] FIG. 3B is a result diagram of a mid-infrared optical frequency comb under the repetition frequency of 609 GHz; and

[0037] FIG. 3C is a result diagram of a mid-infrared optical frequency comb under the repetition frequency of 1.02 THz;

[0038] Numeral symbols: 1—narrow linewidth tunable continuous laser source, 2—power amplifier, 3—attenuator, 4—polarization controller, 5—beam combiner, 6—lithium niobate microcavity, 7—temperature controller, and 8—filter.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present disclosure is further described below in combination with accompanying drawings and specific embodiments.

[0040] Referring to FIG. 1 and FIG. 2, the present embodiment provides a system for generating a mid-infrared optical frequency comb based on a lithium niobate microcavity, including pumping units configured to provide two paths of pumping light, a beam combining unit configured to perform beam combination on the two paths of pumping light, a nonlinear frequency conversion unit configured to undergo a four-wave mixing process and a filter unit configured to filter the remaining pumping light.

[0041] As shown in FIG. 2, the pumping units in the present embodiment are divided into two paths, each pumping unit path includes a narrow linewidth tunable continuous laser source 1, a power amplifier 2, an attenuator 3 and a polarization controller 4 connected in sequence. The beam combining unit is a beam combiner 5 and is configured to perform beam combination on the two paths of pumping light; and in other embodiments, other forms of beam combining devices may also be adopted if only beam combination may be realized. The nonlinear frequency conversion unit includes a lithium niobate microcavity 6 configured to undergo a four-wave mixing effect and a temperature controller 7 configured to adjust the temperature of the lithium niobate microcavity 6. The filtering unit is a filter 8 and is configured to filter the remaining pumping light to obtain a mid-infrared optical frequency comb; and in other embodiments, other forms of filtering devices may also be adopted if only filtration may be realized.

[0042] Specifically, the mid-infrared optical frequency comb may be generated by the following processes:

[0043] 1], the two narrow linewidth tunable continuous laser sources 1 are adjusted to ensure that the wavelength interval of laser emitted by the two laser sources is an integral multiple of a free spectral range of the lithium niobate microcavity 6, and the two beams of laser are taken as signal light of the pumping units;

[0044] 2], intensities of the two paths of signal light are adjusted by the power amplifiers 2 and the attenuators 3 to meet an intensity condition for four-wave mixing (thus, the spectral bandwidth of the output optical frequency comb is maximized); and polarization directions of the two paths of signal light are respectively adjusted by two paths of the polarization controllers 4 to meet the phase matching condition for four-wave mixing; and

[0045] 3], the two paths of adjusted signal light are injected into the lithium niobate microcavity 6 with high nonlinearity and low flattened dispersion after passing through the beam combiner 5, the temperature of the lithium niobate microcavity 6 is adjusted by the temperature controller 7 to meet a resonance condition (the wavelength of injected light is matched with the resonant wavelength of the microcavity) of the microcavity and the phase matching condition for four-wave mixing, and the pumping light undergoes the four-wave mixing effect with high efficiency and low threshold and then passes through the filter 8 to obtain the mid-infrared optical frequency comb to be output.

[0046] The working principle of the present disclosure is that:

[0047] firstly, narrow linewidth tunable continuous laser serves as the pumping light of the nonlinear frequency conversion unit after being subjected to power amplification; and the power of the pumping light is adjusted by the attenuators 3 and the power amplifiers 2 to meet the intensity condition for four-wave mixing, the polarization direction of the pumping light is adjusted by the polarization controllers 4 to meet the phase matching condition for four-wave mixing, the pumping light is injected into the lithium niobate microcavity 6 with high nonlinearity and low flattened dispersion after passing through the beam combiner 5, the temperature of the lithium niobate microcavity 6 is precisely adjusted by the temperature controller 7 to meet the resonance condition of the microcavity and the phase matching condition for four-wave mixing, and the pumping light undergoes the four-wave mixing effect with high efficiency and low threshold and then passes through the filter 8 to obtain the mid-infrared optical frequency comb.

[0048] Referring to FIG. 3A, FIG. 3B and FIG. 3C, the mid-infrared optical frequency comb generation results are provided. The ultrahigh repetition frequency adjustable broadband mid-infrared optical frequency comb with the spectral bandwidth greater than or equal to 1000 nm and the highest repetition-frequency greater than or equal to 1 THz may be achieved by using a double-pump lithium niobate microcavity method. The pumping units are established by using a double-pumping method, the nonlinear frequency conversion unit is established based on the four-wave mixing effect with the high efficiency and the low threshold in the lithium niobate microcavity, and the ultrahigh repetition frequency adjustable broadband mid-infrared optical frequency comb is achieved by controlling parameters such as power, polarization and wavelength of the pumping light. Moreover, the volume, power consumption and the like of a traditional mid-infrared optical frequency comb system may be reduced by several orders of magnitude, and meanwhile, the repetition frequency of the mid-infrared optical frequency comb may reach hundreds of GHz and even THz and is far higher than that of an optical frequency comb generated by a traditional mode locking laser.