CN214751362U

CN214751362U - Low-microwave-power miniature CPT atomic clock light source generating device

Info

Publication number: CN214751362U
Application number: CN202120589139.XU
Authority: CN
Inventors: 王可畏; 徐四六; 何俊荣; 阮诗森; 邓文武
Original assignee: Hubei University of Science and Technology
Current assignee: Hubei University of Science and Technology
Priority date: 2021-03-22
Filing date: 2021-03-22
Publication date: 2021-11-16
Anticipated expiration: 2031-03-22

Abstract

The utility model discloses a miniature CPT atomic clock light source of low microwave power produces device, including direct current generator, microwave generator, biaser, VCSEL, lens, blazed grating, quarter wave plate, direct current generator, microwave generator are connected with the biaser, and the biaser is connected with VCSEL, and lens, blazed grating, quarter wave plate all set up in the light path of VCSEL transmission. The utility model provides a convenient adjustment of chamber length in FP chamber of device, the hyperfine energy level interval of ground state corresponding to different alkali metal atoms consequently can realize different alkali metal atom's miniature CPT atomic clock light source. The utility model discloses the miniature CPT atomic clock light source that obtains compares the required microwave power of conventional scheme and is lower, the limited condition of specially adapted microwave power.

Description

Low-microwave-power miniature CPT atomic clock light source generating device

Technical Field

The utility model belongs to passive Coherent Population Trapping (CPT) atomic clock field, concretely relates to light source produces device and method, utilizes the device and method can realize miniature CPT atomic clock with low microwave power.

Background

The micro CPT atomic clock uses a VCSEL (Vertical Cavity Surface Emitting Laser) modulated by microwave as a light source, generates coherent light to interact with atoms to prepare a CPT state, and obtains a CPT spectral line as a frequency discrimination signal, so that a microwave resonant Cavity is not needed, the micro CPT atomic clock is not limited by the volume of the microwave resonant Cavity, and the micro CPT atomic clock has the advantages of small volume, low power consumption, light weight, quick start and the like. The micro CPT atomic clock has strong application competitiveness in the aspects of a communication network system, a navigation positioning system and the like.

In order to keep the advantage of small volume of the micro CPT atomic clock in the application of an actual CPT atomic clock, the microwave modulation is directly applied to the driving current of the VCSEL, namely, the microwave with the frequency of GHz and direct current are superposed to drive the VCSEL so as to obtain coherent polychromatic light, and a +/-1 order sideband in the polychromatic light is used as coherent bichromatic light, namely, the light source of the micro CPT atomic clock.

The VCSEL is driven by direct current and has an output frequency f₀When a drive current of the VCSEL is applied at a frequency f_mAfter microwave modulation, the VCSEL outputs frequency-modulated polychromatic light, each frequency component being in turn f₀(fundamental frequency) f₀±f_m(sideband of order 1) (+ -), f₀±2f_m(+ -2 order sideband), … …, the frequency difference of adjacent sidebands is f_m. When the VCSEL is modulated by microwave, the total power of laser is kept unchanged, laser energy is transferred from the fundamental frequency to each order of sideband, and the light intensity of each order of sideband is in direct proportion to the square of Bessel coefficient

Wherein I₀For the total intensity of the laser light output from the VCSEL, m_fIs VCSEL microwave modulation index, J_n(m_f) Are coefficients of a bessel function of the first kind.

In practical micro-CPT atomic clock application, in order to make laser energy mainly concentrate on +/-1 order of side band, modulation index m is often adopted_fA shallow modulation of about 1.8. Under shallow modulation conditions, the power of the + -1 order sidebands is approximately proportional to the input microwave signal power.

The utility model provides a low microwave power coherent double-colored light produces scheme compares with conventional device, the utility model provides a device and method can produce miniature CPT atomic clock light source with littleer microwave power.

The utility model has the following contents:

an object of the utility model is to provide a miniature CPT atomic clock light source of low microwave power produces device and method, can realize miniature CPT atomic clock with low microwave power.

In order to achieve the purpose, the utility model adopts the following technical measures:

a low microwave power micro CPT atomic clock light source generating device comprises a direct current generator, a microwave generator, a biaser, a VCSEL (vertical cavity surface emitting laser), a lens, a blazed grating and a quarter wave plate;

the direct current generator and the microwave generator are respectively connected with the biaser, and the biaser is connected with the VCSEL; the lens, the blazed grating and the quarter wave plate are all arranged in a light path emitted by the VCSEL;

direct current generated by the direct current generator and microwaves generated by the microwave generator are superposed through the biaser and then drive the VCSEL to generate divergent light, the divergent light is converted into parallel light beams through the lens, the blazed grating is configured into a Littrow structure, the parallel light beams are diffracted when passing through the blazed grating, first-order diffracted light returns to the VCSEL along the original path to realize external cavity feedback, and zero-order diffracted light is used as device output light beams.

For the sake of clarity, the present invention is further explained below:

as shown in FIG. 1, the VCSEL4 structure includes a bottom mirror 4(1) and a top mirror 4(2), where the bottom mirror 4(1) is a fully reflective mirror, the top mirror 4(2) is a partially reflective partially transmissive mirror, and the bottom mirror 4(2) is a partially reflective partially transmissive mirrorThe partial mirror 4(1) and the top mirror 4(1) constitute an optical FP (Fabry Perot, FP) cavity, which is the active region of the VCSEL. The blazed grating 6 is configured into a Littrow structure as an external feedback element, laser generated by the VCSEL4 is diffracted when passing through the blazed grating 6, first-order diffracted light returns to an active region of the VCSEL along an original light path, and at the moment, the blazed grating 6 and a bottom mirror 4(1) of the VCSEL4 form a new composite FP cavity. The cavity length of the composite FP cavity is L_eff＝L_vcseln_vcsel+L_lenn_len+L_airn_airWherein L is_VCSEL、L_len、L_airLength of active region, length of lens 5, light at L of VCSEL4 respectively_effLength of propagation in air, n_VCSEL、n_len、n_airThe VCSEL4 active region index, lens 5 material index, and air index, respectively. The resonant frequency of the composite FP cavity is

Wherein C is the speed of light and q is a positive integer. Setting the appropriate chamber length L_effThe resonant frequency of the composite FP cavity can be made equal to the microwave modulation frequency, i.e. f_q＝f_mDue to the feedback effect of the blazed grating 6 and the frequency selection effect of the composite FP cavity, a coherent bicolor light source required by the micro CPT atomic clock can be obtained with lower microwave power.

Compared with the prior art, the utility model has the advantages of it is following:

(1) the FP chamber length L of the device of the utility model_effThe micro CPT atomic clock is convenient to adjust, has different hyperfine energy level intervals corresponding to the ground state of the alkali metal atoms, and can be suitable for realizing micro CPT atomic clocks with different alkali metal atoms.

(2) The utility model provides a miniature CPT atomic clock light source that the device obtained compares the required microwave power of conventional scheme and is lower, the limited condition of specially adapted microwave power.

Drawings

Fig. 1 is a schematic structural diagram of a low microwave power micro CPT atomic clock light source generating device, wherein 1-a direct current generator, 2-a microwave generator, 3-a biaser, 4-a VCSEL, 5-a lens, 6-a blazed grating and 7-a quarter wave plate.

Fig. 2 is a comparison graph of the percentage of the effective sideband power (+/-1 order sideband power) in the light source generated by the device and the free running VCSEL to the total laser power according to the variation of the microwave power under the same microwave power condition. Wherein the circular solid line represents the percentage of the effective sideband power in the light source obtained using the device of the invention and the square dotted line represents the percentage of the effective sideband power in the light source obtained using the free running VCSEL.

Detailed Description

To facilitate understanding and practice of the invention for those skilled in the art, the following detailed description of the invention is provided in connection with the accompanying drawings and the embodiments, it being understood that the embodiments described herein are merely illustrative and explanatory of the invention and are not restrictive thereof.

This example adopts⁸⁷The technical scheme of the present invention is further described in detail by taking the Rb atom as an example.

As shown in fig. 1, the utility model provides a low microwave power miniature CPT atomic clock light source generating device, which comprises a direct current generator 1, a microwave generator 2, a bias device 3, a VCSEL4, a lens 5, a blazed grating 6 and a quarter wave plate 7; the direct current generator 1 and the microwave generator 2 are respectively connected with a biaser 3, and the biaser 3 is connected with the VCSEL 4; the lens 5, the blazed grating 6 and the quarter-wave plate 7 are all arranged in an optical path emitted by the VCSEL 4; direct current generated by the direct current generator 1 and microwaves generated by the microwave generator 2 are superposed through the biaser 3 to drive the VCSEL4 to generate divergent light, the divergent light becomes parallel light after passing through the lens 5, output light of the VCSEL4 and the blazed grating 6 form a Littrow structure, namely when the divergent light output by the VCSEL4 becomes parallel light after passing through the blazed grating 6 through the lens 5, first-order diffraction light generated by diffraction returns to an active area of the VCSEL4 along an original path to realize feedback, and zero-order diffraction light generated by diffraction is used as output light.

In practical application, can utilize the utility model provides a device realizes the miniature CPT atomic clock light source of low microwave power, including following operating procedure:

(1) as shown in figure 1 of the drawings, in which,the frequency generated by the microwave generator 2 is f_m3.4Ghz microwave and direct current generated by the direct current generator 1 are superposed through the biaser 3 to drive the VCSEL4, the VCSEL4 outputs frequency-modulated multicolor linearly polarized light, and the position of the lens 5 in the Z direction is adjusted, so that divergent light output by the VCSEL4 is changed into parallel light beams through the lens 5 and is output;

(2) the blazed grating 6 of this embodiment is of the type THORLABS GR13-1208, and the angle of the blazed grating 6 in the XZ plane is adjusted, so that the blazed grating 6 forms a Littrow structure, that is, when divergent light output by the VCSEL4 is changed into parallel light beams through the lens 5 and passes through the blazed grating 6, first-order diffracted light generated by diffraction returns to an active region of the VCSEL4 along an original path to realize feedback, and zero-order diffracted light generated by diffraction is used as output light beams. The angle of the blazed grating 6 in the XZ plane is kept constant in subsequent operations.

(3) Adjusting the microwave power generated by the microwave generator 2 to zero, and gradually increasing the direct current generated by the direct current generator 1 to the VCSEL4 to emit light normally; the position of the blazed grating 6 in the Z direction is adjusted, the output beam of the blazed grating 6 is detected by using a scanning FP interferometer (the scanning FP interferometer of this embodiment is THORLABS SA210), and when it is detected that the frequency difference of ± 1-order sidebands of the output beam is equal to 6.8GHz, the position of the blazed grating 6 in the Z direction is kept unchanged.

(4) The frequency generated by the microwave generator 2 is f_mThe microwave that 3.4Ghz is No. and the direct current that direct current generator 1 produced drive VCSEL4 after passing through the stack of biaser 3, adjusts quarter wave plate 7 at the planar angle of XY, makes the linear polarization through quarter wave plate 7 become circular polarized light output, obtains promptly the utility model provides a miniature CPT atomic clock light source.

Fig. 2 is a comparison graph of the percentage of the effective sideband power (+/-1 order sideband power) in the light source generated by the device and the free running VCSEL to the total laser power according to the variation of the microwave power under the same microwave power condition. Wherein the circular solid line represents the percentage of the effective sideband power in the light source obtained using the device of the invention and the square dotted line represents the percentage of the effective sideband power in the light source obtained using the free running VCSEL. As can be seen from FIG. 2, when the VCSEL runs freely, the microwave power required when the VCSEL outputs a 10% sideband power of + -1 order is-4 dBm, and when external grating feedback exists, the required microwave power is reduced to-16 dBm. In addition, when external grating feedback exists, the proportion of +/-1 order sideband power obtained by microwave modulation is more than 50% in a wider microwave power range of-8 dBm to 2 dBm. The result shows that the micro CPT atomic clock light source obtained by the utility model requires lower microwave power compared with the conventional scheme.

It should be understood that the above description of the preferred embodiments is given in some detail, and not as a limitation to the scope of the invention, and that various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

1. A low microwave power miniature CPT atomic clock light source generating device is characterized in that: the device comprises a direct current generator, a microwave generator, a biaser, a VCSEL (vertical cavity surface emitting laser), a lens, a blazed grating and a quarter-wave plate;

2. A low microwave power micro CPT atomic clock light source generating device as claimed in claim 1, wherein: the angle of the blazed grating in the XZ plane is adjusted, laser light generated by the VCSEL is incident on the blazed grating at an incident angle θ, and the blazed grating is configured in a Littrow structure when the incident angle θ is adjusted to be equal to the blazed angle of the blazed grating.