[0046] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific implementations of the present invention are now described. It should be understood that the specific embodiments described here are only used to explain the present invention, and are not intended to limit the present invention, that is, the described embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.
[0047] This embodiment provides a volume holographic material sensitivity testing device and method with different spot sizes, such asfigure 1 As shown, the test device includes a coherent light source 1, an interference light path, a first photodetector 3, a second photodetector 4, an acquisition card 5 and a host computer 6, the coherent light source 1 is used to provide coherent light, and the interference light path combines the coherent light source The coherent light provided by 1 is divided into two beams and interferes at the position of the volume holographic material 7, the first photodetector 3 and the second photodetector 4 are used to detect the intensity of the interfered beam in the interference optical path, and the acquisition card 5 For collecting the voltage signals output by the first photodetector 3 and the second photodetector 4 and converting them into digital signals, the host computer 6 is used for processing and storing the digital signals obtained by the acquisition card 5, wherein:
[0048] The interference optical path includes a first electronic shutter 21, a first diaphragm 23, a first half-wave plate 24, a polarization beam splitter prism 25, a second electronic shutter 26, a second half-wave plate 27 and a second diaphragm 30, and the coherent light source 1 provides The coherent light can be divided into two beams after passing through the first electronic shutter 21, the first aperture 23, the first half-wave plate 24 and the polarizing beam splitter prism 25 in sequence, that is, the coherent light passes through the first aperture 23 to reach the desired beam size, adjust the polarization state through the first half-wave plate 24, and then be divided into two beams after passing through the polarization beam splitter 25 (PBS) (the beam splitting ratio can be adjusted by the first half-wave plate 24), wherein the first beam passes through After the second electronic shutter 26 is irradiated onto the volume holographic material 7, the second light beam first passes through the second half-wave plate 27, and then is reduced in size by the second aperture 30 and then irradiates on the volume holographic material 7, so that the formed light spot falls Into the larger light spot formed by the first light beam, the two light beams are transmitted through the volume holographic material 7 and then detected by the first photodetector 3 and the second photodetector 4 respectively.
[0049] In a preferred embodiment of the present invention, the interference optical path further includes a beam expander 22, the beam expander 22 is arranged between the first electronic shutter 21 and the first half-wave plate 24, and the coherent light is expanded by the beam expander 22 , and then through the first aperture 23 aperture to reach the required beam size.
[0050] In a preferred embodiment of the present invention, the interference optical path further includes a first lens 28 and a second lens 29, the first lens 28 is arranged in front of the first photodetector 3, and the second lens 29 is arranged in the second photodetector 4 ahead.
[0051] In a preferred embodiment of the present invention, the coherent light source 1 adopts a continuous laser with a coherence length greater than 20 millimeters, specifically a single longitudinal mode green laser of MSL-III-532, the first photodetector 3 and the second photodetector The detector 4 can be a silicon-based detector with a model number of PDA36A2, and the upper computer 6 can be realized by a computer.
[0052] A method for testing the sensitivity of volume holographic materials with different spot sizes provided in this embodiment includes the following steps:
[0053] The coherent light provided by the coherent light source 1 is divided into two light beams after passing through the first electronic shutter 21, the first aperture 23, the first half-wave plate 24 and the polarization beam splitter 25 in sequence, that is, the coherent light passes through the first aperture 23 Reach the required beam size, adjust the polarization state through the first half-wave plate 24, and then be divided into two beams after passing through the polarization beam splitter 25 (PBS) (the beam splitting ratio can be adjusted by the first half-wave plate 24), wherein the first One light beam passes through the second electronic shutter 26 and irradiates the volume holographic material 7, and the second light beam first passes through the second half-wave plate 27, and then is shrunk by the second aperture 30 to irradiate the volume holographic material 7, so that The formed light spot falls into the larger light spot formed by the first light beam, and the two light beams are transmitted through the volume holographic material 7 and then detected by the first photodetector 3 and the second photodetector 4 respectively;
[0054] When measuring, the first electronic shutter 21 receives the control signal of the host computer 6 and opens, the second electronic shutter 26 is opened and closed periodically, and the acquisition card 5 enters the acquisition state, and the host computer 6 enters the data storage state.
[0055] The diffraction efficiency and transmittance of the volume holographic material 7 can be calculated based on the intensity detection results of the first photodetector 3 and the second photodetector 4, including the steps of: recording background signals, calculating the ratio of the amplification factor, collecting real-time data, and calculating the diffraction efficiency and calculate the transmittance, where:
[0056] 1. The step of recording the background signal includes the following sub-steps:
[0057] Assuming that the measured signal P is composed of the amplification factor m, the background b and the spot area s, that is
[0058] P=m[sp(t)+b] (1)
[0059] The volume holographic material 7 is not placed, and the first electronic shutter 21 is closed, so p(t)=0, at this time, the signal B received by the first photodetector 3 and the second photodetector 4 1 , B 2 The background noise is the product of the background b and the amplification factor m:
[0060] B 1 = m 1 b 1 (2)
[0061] B 2 = m 2 b 2 (3).
[0062] 2. The step of calculating the ratio of the amplification factor includes the following sub-steps:
[0063] The volume holographic material 7 is not placed, and the first electronic shutter 21 and the second electronic shutter 26 are opened at the same time, so the optical power density received by the first photodetector 3 and the second photodetector 4 is the same, that is, p 1 (t)=p 2 (t)=p 0 , the output signals of the first photodetector 3 and the second photodetector 4 are:
[0064]
[0065]
[0066] By formula (2)~(5), the amplification factor m of the first photodetector 3 and the second photodetector 4 1 、m 2 The ratio is:
[0067]
[0068] 3. The step of collecting real-time data includes the following sub-steps:
[0069] Place the volume holographic material 7, open the first electronic shutter 21, and let the second electronic shutter 26 be in the periodic switching state; when the second electronic shutter 26 is closed, the transmitted beam and the diffracted beam have the same diameter, and the first photodetector 3 and the output signal of the second photodetector 4 are:
[0070] P 1 (t)=m 1 [s 1 p 1 (t)+b 1 ] (7)
[0071] P 2 (t)=m 2 [s 1 p 2 (t)+b 2 ] (8).
[0072] 4. The step of calculating the diffraction efficiency includes the following sub-steps:
[0073] According to the calculation formula of diffraction efficiency to eliminate the absorption effect:
[0074]
[0075] Then, according to formulas (6) to (9), the diffraction efficiency expression represented by the measured value is derived:
[0076]
[0077] 5. The step of calculating the transmittance includes the following sub-steps:
[0078] Formulas (7), (8) are expressed as expressions based on diffraction efficiency and transmittance
[0079] P 1 (t)=m 1 [s 1 p 0 T(t)(1-η)+b 1 ] (11)
[0080] P 2 (t)=m 2 [s 1 p 0 T(t)η+b 2 ] (12)
[0081] The formula (11), (12) eliminate the diffraction efficiency η to obtain the transmittance expression given by the measured value
[0082]
[0083] In a preferred embodiment of the present invention, according to the "record background signal" step, the volume holographic material 7 is not placed, the first electronic shutter 21 is closed, and the signal B received by the first photodetector 3 and the second photodetector 4 1 , B 2 They are 0.0083V and 0.0149V respectively; according to the step of "calculating the ratio of the amplification factor", the volume holographic material 7 is not placed, and the first electronic shutter 21 and the second electronic shutter 26 are opened at the same time, the first photodetector 3 and the second photodetector 4 Received signals: 2.5024V and 6.4640V respectively; according to the step of "collecting real-time data", place the volume holographic material 7, open the first electronic shutter 21, and let the second electronic shutter 26 be in the periodic switch state; when the second electronic shutter 26 is closed, the second electronic shutter 26 The output signals of a photodetector 3 and the second photodetector 4 are respectively as figure 2 , 3 shown.
[0084] Will figure 2 , 3 The data in and the background signal, Substituting Equation (10) and Equation (13) to obtain the diffraction efficiency and transmittance respectively, as Figure 4 , 5 shown.
[0085] Through the method in this patent, the relationship between diffraction efficiency and time, and the relationship between diffraction efficiency and transmittance are given quantitatively. Since only the small light spot needs to "fall into" the large light spot, there is no need for precise "overlap" adjustment, so it has better operability and reliability.
[0086] The above descriptions are only preferred embodiments of the present invention, and it should be understood that the present invention is not limited to the forms disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and Modifications can be made within the scope of the ideas described herein, by virtue of the above teachings or skill or knowledge in the relevant art. However, changes and changes made by those skilled in the art do not depart from the spirit and scope of the present invention, and should all be within the protection scope of the appended claims of the present invention.
[0087] In the description of the present invention, it should be noted that the terms "first", "second", "third" and so on are only used to distinguish descriptions, and should not be understood as indicating or implying relative importance.
