CN103149708A - Any field polarization state control system - Google Patents

Abstract

The invention discloses an any field polarization state control system, which is an optical system for controlling any field distribution light field polarization state. In the system, a polarization control panel manufactured by using an electro-optical crystal array is used, so that polarization control of incident laser beams is realized, incident laser light is converted into a predicted polarization state, and incident laser light can even be converted into non-polarized light; and the any field polarization state control system can be applied to an ICF (Inter-Communication Flip-Flop) driver cavity, multi-beam depolarization is realized, and uniform irradiation of a target surface is realized.

Description

Arbitrary Field Polarization State Control System

technical field

The invention relates to an optical system capable of controlling the polarization state of an arbitrary field distribution light field. The system can convert any field distribution light field into the expected polarization state such as unpolarized light, and even completely eliminate the polarization state of the light field, which will help reduce the sub-beam interference speckle in the spot in the ICF device, for example, Thereby achieving the purpose of smoothing the laser beam.

Background technique

For laser devices that realize inertial confinement fusion (ICF, Inertial Confinement Fusion), the polarization of the beam focused on the target surface means that the vibration direction of the electric field component in the light field is perpendicular to the propagation direction. In the plane perpendicular to the light propagation, the electric field component (also known as the light vector) has different vibration states, which correspond to different polarization states. Polarized light beams have many practical uses. For example, using two beams of orthogonal electromagnetic waves of the same frequency in satellite communication and optical fiber communication can double the transmission rate of the signal; biological and chemical scientists use the difference in the absorption rate of left-handed and right-handed circularly polarized light to detect enantiotropic Chemical molecules or biological macromolecules with conformational characteristics; laser beams of different polarization states are also used in quantum cryptography; in non-invasive laser diagnosis and treatment diagnostic technology, polarized light imaging is also a very cutting-edge application; in the pathology of biological tissues In the optical detection technology of sexual lesions, the information of the output light field contains the polarization parameter of the field (that is, the polarization state). In addition, for inertial confinement fusion (ICF, Inertial Confinement Fusion) laser devices, it is necessary to convert the incident laser light into unpolarized light to achieve the purpose of depolarization, which is beneficial to achieve uniform irradiation of the target surface. At present, there are many types of polarization controllers, but the principle is to make the two components of a polarization state produce different phase delays through the birefringence effect, so as to regenerate the expected polarization state. According to its technical principle, polarization controllers can be roughly divided into three categories: azimuth control type, delay control type and azimuth-delay control type. However, this type of polarization controller has many disadvantages, such as the high cost of components such as wave plates and microlenses, and the need for anti-reflection coatings to reduce reflection losses, and the wave plates are sensitive to wavelengths. Later, an all-fiber polarization controller based on the same principle appeared, which has small loss and low cost, but is still sensitive to wavelength and has a slow control speed. The polarization controllers such as liquid crystal type, electro-optic crystal type, and piezoelectric ceramic variable and switchable wave plate type have been proposed one after another, but there are some insurmountable shortcomings, so the research on polarization controllers has been in progress. In order to transform the polarization state of any light field into any desired polarization state, we propose a novel polarization control system.

Contents of the invention

At present, there is no report on the control system of the polarization state of the arbitrary light field, but the polarization state of the light field is an extremely important physical quantity in modern optical applications, such as in the ICF device, it is necessary to overcome the existing polarization smoothing technology The deficiency of the interference pattern of the sub-beams cannot be eliminated, and this system is proposed by us based on this. The light field polarization state control system in the present invention can realize the polarization control of any light field, and even convert the incident laser light into non-polarized light, so as to avoid the interference of sub-beams when the light beam is focused, so as to achieve the purpose of beam smoothness.

The technical solution of the present invention is: there is an optical field polarization state control array plate in the system device, the plate plays the role of polarization control, and is composed of p×q processing units, and each unit is equipped with a controllable electro-optic crystal, such as KDP crystals. By adding an appropriate voltage, the electro-optic crystal plate produces a suitable phase delay for the two components of the incident polarized light, so that the outgoing light becomes the polarized light we need, and the purpose of modulating the polarization state of the incident beam is achieved. When the laser passes through the polarization control array plate, it is divided into many sub-beams, and the amplitude and phase of each sub-beam are modulated to different degrees. Therefore, when the laser passes through the light field polarization state control array plate and then transforms into the target light field, it can also achieve complete unpolarized light. The speckle can be eliminated, so that the uniform irradiation of the target surface can be realized.

Compared with the existing polarization control technology, the present invention has the advantage that the polarization state of each sub-beam of the incident arbitrary field distribution light field can be effectively controlled by controlling the voltage applied to each unit chip, and then converted into expected polarization state. For example, arbitrary light fields can be converted to unpolarized light. The main component in the system device is the optical field polarization state control array plate, which is easy to manufacture and simple in structure.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 is a schematic diagram of the device of the present invention.

Fig. 2 is a schematic diagram of an optical field polarization state control array plate.

Fig. 3 is a schematic diagram of a first embodiment of an optical field polarization state control array plate.

Fig. 4 is a schematic diagram of a second embodiment of an optical field polarization control array plate.

In Figure 1, 1 phase modulator, 2 gratings, 3 light field polarization state control array plate, 4 focusing lens, 5 target surface for receiving light field

The optical field polarization control array plate in Fig. 2 is a p×q controllable optical rotation crystal array.

The optical field polarization state control array plate in Fig. 3 is a random polarizing plate.

The optical field polarization control array plate in Fig. 4 is a crossed polarizer.

specific implementation plan

In Embodiment 1 of the present invention, the optical field polarization control array plate is a random polarizing plate, as shown in FIG. 3 . The phase-modulated light field undergoes dispersion after passing through the grating, and is divided into multiple sub-beams after passing through a random polarizing plate, and their respective polarization states change randomly, and finally focus on the target surface through the lens. A random polarizing plate is used to generate sub-beams with different polarization states inside the large-aperture beam by changing the polarization state of each sub-unit beam.

When the laser beam is transmitted through the system, the spectrum broadening and grating dispersion in the spectral dispersion smoothing technology make the interference speckle generated by the sub-beams of each frequency shift in the direction of dispersion, thus realizing the focus spot on the time average scale smooth. The main effect of the use of the polarization state control array plate on the field distribution of the focal spot is that the amplitude modulation and phase of different wavelengths superimposed in the x and y directions are different, so that the polarization states of the output light at different wavelengths are different, resulting in a significant change in the polarization state of the beam The change achieves depolarization.

Embodiment 2 of the present invention, the optical field polarization control array plate is an orthogonal polarizing plate, as shown in FIG. 4 . For the crossed polarizing plates, the outgoing light beams of each subunit can only be linearly polarized light in a certain polarization direction.

Claims (3)

1. one kind can be used for optical processing system that any field distribution light field polarization state of incident is controlled, formed by position phase control device, grating, light field polarization state control array board and lens, it is characterized in that: after incident laser passes through position phase control device and grating, make the interference speckle of the beamlet generation of each frequency produce displacement on dispersion direction, control array board by the light field polarization state again, the wavelet of different wave length is carried out different amplitudes and position modulation mutually, make output light in the polarization state difference at different wave length place, to obtaining the polarization state of expection.

2. light field polarization state according to claim 1 is controlled array board, it is characterized in that: the light field polarization state is controlled array board and is comprised p * q processing unit, and each processing unit is placed a controlled electro-optic crystal.

3. controlled electro-optic crystal according to claim 2, it is characterized in that: can make the electro-optic crystal sheet produce to two components of incident polarized light the bit phase delay that is fit to by adding suitable voltage, thereby make emergent light become the polarized light of expection, reach the purpose of modulated incident light beam polarization state.

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