Bi-pass modulation light path based on quartz acousto-optic modulator

Abstract

The utility model belongs to the technical field of photoelectronics, and relates to a bi-pass modulation light path based on a quartz acousto-optic modulator, and the dielectric material of the acousto-optic modulator in the bi-pass modulation light path is quartz crystal; the quartz crystal can enable the polarization direction of the passing light beam to rotate by 45 degrees + N * 90 degrees; according to the invention, the polarization direction of diffracted light is rotated by 45 degrees + N * 90 degrees by the acousto-optic modulator by using the optical rotation characteristic of a quartz crystal, the diffracted light is reflected and then passes through the acousto-optic modulator to generate secondary frequency shift, and the polarization direction of the secondary diffracted light is rotated by 45 degrees + N * 90 degrees, so that the light returned to the polarization beam splitter prism is perpendicular to the polarization state of the incident light, and the polarization of the incident light is realized. The frequency shift amount twice the driving frequency of the acousto-optic modulator is integrally realized, and the quartz crystal is used as a dielectric material, so that the laser tolerance power of a bi-pass modulation light path is improved, and the light passing area of the bi-pass modulation light path is widened.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technology and relates to a double-pass modulation optical path based on a quartz acousto-optic modulator. Background Art

[0002] An acousto-optic modulator, also known as an acousto-optic frequency shifter, is a device that uses acousto-optic interaction to achieve laser frequency shifting and is widely used in fields such as laser frequency stabilization, laser heterodyne interferometry, cold atoms, and ion traps. When a laser passes through an acousto-optic modulator, diffraction occurs, and there is a shift in the radio frequency signal frequency between the diffracted light and the zero-order light. When the acousto-optic interaction is positive frequency shifting, the frequency of the diffracted light increases and is the sum of the incident light and radio frequency signal frequencies; when the acousto-optic interaction is negative frequency shifting, the frequency of the diffracted light decreases and is the difference between the incident light and radio frequency signal frequencies.

[0003] The light beam undergoes frequency shifting once through the diffracted light of the acousto-optic modulator, while the double-pass method can perform diffraction twice by one acousto-optic modulator, and the frequency shift amount is twice the driving frequency of the acousto-optic modulator, achieving a higher frequency shifting effect and effective utilization of the driving power.

[0004] Currently, the acousto-optic modulators commonly used for double-pass modulation mainly use tellurium oxide materials as the acousto-optic medium. The tellurium oxide acousto-optic modulator can produce acousto-optic diffraction with light of any polarization direction; however, the tellurium oxide crystal has a low tolerance for laser power, and the light passing region is cutoff at about 350 nm. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the present invention proposes a double-pass modulation optical path based on a quartz acousto-optic modulator, including:

[0006] A laser 1, a λ / 2 wave plate 2, a polarization beam splitter prism 3, an acousto-optic modulator 4, a focusing lens 5, a λ / 4 wave plate 6, a mirror 7, and a radio frequency driver 8. The acousto-optic modulator 4 includes an acousto-optic medium 11, and the acousto-optic medium 11 is a quartz crystal.

[0007] The quartz crystal can rotate the polarization direction of the passing light beam by 45° + N×90°; where N is an integer.

[0008] The acousto-optic modulator 4 further includes: a bonding layer 12, a transducer 13, a surface electrode 14, a matching network 15, a device housing 16, and a radio frequency connector 17; the transducer 13 is disposed on the surface of the acousto-optic medium 11 through the bonding layer 12; the surface electrode 14 is disposed on the surface of the transducer 13 and is connected to the matching network 15; the radio frequency connector 17 is fixed on the device housing 16 and is connected to the matching network 15.

[0009] Thermal conductive glue is uniformly disposed on the upper and lower surfaces of the acousto-optic medium 11.

[0010] A water-cooled plate is placed below the acousto-optic modulator 4.

[0011] Advantages of the present invention:

[0012] 1. In the double-pass modulation optical path of the present invention, the medium material of the acousto-optic modulator is a quartz crystal. The acousto-optic modulator utilizes the optical rotation characteristic of the quartz crystal to rotate the polarization direction of the diffracted light by 45° + N×90°. After being reflected by the mirror, it passes through the acousto-optic modulator again to generate a second frequency shift. At the same time, the polarization direction of the second diffracted light rotates by 45° + N×90° again, so that the light returning to the polarization beam splitter prism is perpendicular to the polarization state of the incident light, effectively separating the diffracted light after the second frequency shift. The overall frequency shift amount is twice the driving frequency of the acousto-optic modulator, and using the quartz crystal as the medium material improves the laser power tolerance of the double-pass modulation optical path and broadens the light passing area of the double-pass modulation optical path; 2. The double-pass modulation optical path of the present invention only uses one acousto-optic modulator, and diffraction is carried out by the beam passing through twice, effectively utilizing the driving power of the device and reducing the electrical power requirement. Description of the drawings

[0013] Figure 1 It is a schematic diagram of a double-pass modulation optical path based on a quartz acousto-optic modulator provided by an embodiment of the present invention;

[0014] Figure 2 It is a schematic diagram of the structure of the acousto-optic modulator provided by an embodiment of the present invention;

[0015] Among them, 1. Laser; 2. λ / 2 wave plate; 3. Polarization beam splitter prism; 4. Acousto-optic modulator; 5. Focusing lens; 6. λ / 4 wave plate; 7. Mirror; 8. RF driver; 9. Zero-order light; 10. First-order diffracted light; 11. Acousto-optic medium; 12. Bonding layer; 13. Transducer; 14. Surface electrode; 15. Matching network; 16. Device housing; 17. RF connector. Specific embodiments

[0016] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0017] As Figure 1 shown, the present invention adopts a double-pass modulation optical path based on a quartz acousto-optic modulator, including: a laser 1, a λ / 2 wave plate 2, a polarization beam splitter prism 3, an acousto-optic modulator 4, a focusing lens 5, a λ / 4 wave plate 6, a mirror 7, and an RF driver 8.

[0018] The laser 1 outputs linearly polarized light. The linearly polarized light is adjusted to horizontally polarized light by the λ / 2 wave plate 2. The horizontally polarized light completely passes through the polarization beam splitter prism 3 and is incident on the acousto-optic modulator 4 at a certain angle to undergo diffraction for the first frequency shift. After exiting, the polarization directions of the zero-order light 9 and the first-order diffracted light 10 rotate by 45° + N×90°; the acousto-optic modulator 4 is located at the focal point of the focusing lens 5, so both the zero-order light 9 and the first-order diffracted light 10 become parallel light after passing through the focusing lens 5; the λ / 4 wave plate 6 is located on the optical path of the parallel first-order diffracted light 10, and the mirror 7 is located behind the λ / 4 wave plate 6 and is vertically placed on the optical path of the parallel first-order diffracted light 10. Then, after the parallel first-order diffracted light 10 passes through the λ / 4 wave plate 6, it is reflected by the mirror 7 and returns along the original optical path. When passing through the λ / 4 wave plate 6 twice, the polarization state of the light beam rotates by 90°. It undergoes diffraction again through the acousto-optic modulator 4 for the second frequency shift, and at the same time, the polarization direction of the light beam rotates by 45° + N×90° again. Therefore, the light returning to the polarization beam splitter prism 3 along the original optical path of the incident light becomes vertically polarized light, and the optical path turns and exits. The total frequency shift amount is twice the driving frequency of the acousto-optic modulator; the radio frequency driver 8 provides a modulation signal to the acousto-optic modulator 4.

[0019] As Figure 2 shown, the acousto-optic modulator includes: an acousto-optic medium 11, a bonding layer 12, a transducer 13, a surface electrode 14, a matching network 15, a device housing 16, and a radio frequency connector 17; the acousto-optic medium 11 is made of quartz crystal material, and the transducer 13 is arranged on the surface of the acousto-optic medium 11 through the bonding layer 12; the surface electrode 14 is arranged on the surface of the transducer 13 and is connected to the matching network 15; the radio frequency connector 17 is fixed on the device housing 16 and is connected to the matching network 15.

[0020] Further, the acousto-optic modulator of the present invention uses quartz crystal material as the acousto-optic medium. In order to make the polarization direction of the light rotate by θ = 45° after passing through the quartz crystal, the length of the quartz crystal where N is an integer and α is the optical rotation rate of the quartz crystal. The optical rotation rate α of the quartz crystal material under different wavelengths can be obtained through experimental measurement.

[0021] Furthermore, if the output of the laser 1 is circularly polarized or elliptically polarized, a λ / 4 wave plate can be added after the light source first to change the light beam into linearly polarized light.

[0022] The optical wavelength of the present invention can be any wavelength in the ultraviolet, visible, and infrared bands, such as 355 nm, 411 nm, 633 nm, etc.;

[0023] In one embodiment, at a laser wavelength of 405 nm, the length of the quartz crystal is 53 mm.

[0024] In one embodiment, a thermal conductive adhesive with good thermal conductivity is uniformly disposed on the upper and lower surfaces of the quartz crystal for heat dissipation. Meanwhile, a water-cooling plate is placed under the acousto-optic modulator to keep the device temperature stable at room temperature, so as to reduce the influence of temperature on the optical rotation of the quartz crystal.

[0025] In one embodiment, when the radio frequency driving signal is 150 MHz, the frequency shift amount of the diffracted light after double-pass modulation reaches 300 MHz.

[0026] The above-described embodiments further elaborate on the object, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made to the present invention within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A double-pass modulation optical path based on a quartz acousto-optic modulator, comprising: Laser (1), λ / 2 wave plate (2), polarization beam splitting prism (3), acousto-optic modulator (4), focusing lens (5), λ / 4 wave plate (6), mirror (7) and radio frequency driver (8), the acousto-optic modulator (4) includes an acousto-optic medium (11), characterized in that the acousto-optic medium (11) is a quartz crystal.

2. The double-pass modulation optical path based on a quartz acousto-optic modulator according to claim 1, wherein The quartz crystal can rotate the polarization direction of the passing light beam by 45° + N×90°; where N is an integer.

3. A double-pass modulation optical path based on a quartz acousto-optic modulator according to claim 1, characterized in that, The acousto-optic modulator (4) further includes: a bonding layer (12), a transducer (13), a surface electrode (14), a matching network (15), a device housing (16) and a radio frequency connector (17); the transducer (13) is disposed on the surface of the acousto-optic medium (11) through the bonding layer (12); the surface electrode (14) is disposed on the surface of the transducer (13) and is connected to the matching network (15); the radio frequency connector (17) is fixed on the device housing (16) and is connected to the matching network (15).

4. A double-pass modulation optical path based on a quartz acousto-optic modulator according to claim 1, characterized in that, Thermal conductive glue is uniformly disposed on the upper and lower surfaces of the acousto-optic medium (11).

5. A double-pass modulation optical path based on a quartz acousto-optic modulator according to claim 1, characterized in that, A water cooling plate is placed below the acousto-optic modulator (4).

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