HsienHui Cheng, Achintya K. Bhowmik, and Philip J. Bos, "Analysis of a dual-twist Pancharatnam phase device with ultrahigh-efficiency large-angle optical beam steering," Appl. Opt. 54, 10035-10043 (2015)
It has been previously shown that a Pancharatnam phase device with a dual-twist structure can deflect light up to 60° with nearly perfect efficiency. This was beyond the limits previously assumed for these types of devices, which were considered to be optically similar to Raman–Nath gratings. In this paper we first consider the range of parameters that will allow for high efficiency and show the results for a structure that demonstrates 80° deflection. We then explore the light propagation through these devices to point out interesting intensity variations in the deflected mode of light as it traverses the deflecting layer. Finally, we explain the key to understanding the efficiency of these devices, which is not the typical parameters that are important for traditional diffractive devices, but rather the control of the polarization state of light. We provide a simple design approach for optimizing the twist angle and retardation for high efficiency.
Kun Gao, Colin McGinty, Harold Payson, Shaun Berry, Joseph Vornehm, Valerie Finnemeyer, Brian Roberts, and Philip Bos Opt. Express 25(6) 6283-6293 (2017)
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Total width of grating source layer to computation region grids computation region to NFFF layer
Far-Field Screen
distance between PG and far field screen , angular resolution of far-field screen
Table 2.
(a) Optimized On-Axis Twist Angle for DTPPDs at Different Deflection Angles and Different Birefringence, (b) Optimized Value of nd for DTPPDs at Different Deflection Angles and Different Birefringence, (c) Range of nd for Optimized DTPPDs Where Intrinsic Diffraction Efficiency Is Larger Than 90%, (d) On-Axis Twist Angle Range Where Intrinsic Diffraction Efficiency of DTPPDs Can Be Larger Than 95% by Optimization of Value of nd
(a) Optimized on-axis Twist Angle
\ Deflection Angle
0.106
60
120
250
320
0.179
55
75
160
180
0.3
40
60
85
130
(b) Optimized value of nd ()
\ Deflection Angle
0.106
0.179
0.3
(c) nd range where intrinsic diffraction efficiency for optimized ()
\ Deflection Angle
0.106
0.179
0.3
(d) angle where intrinsic diffraction efficiency can be (°)
We estimate range simply by the other side.
It can have a high efficiency range that is much wider than the range of our simulation.
Due to the precision of our simulation parameters, the maximum efficiency is slightly less than .
Table 3.
(a) Simulation Result of Intrinsic Diffraction Efficiency of Optimized DTPPDs, (b) Device Efficiency of Optimized DTPPDs, (c) Theoretical Transmission Due to Loss of Reflection by Fresnel Equation
(a) Optimized Intrinsic Diffraction Efficiency
\ Deflection Angle
0.106
99.53%
98.44%
98.93%
95.27%
0.179
99.54%
99.29%
99.22%
94.55%
0.3
99.12%
98.90%
99.31%
95.82%
(b) Device Efficiency for optimized DLPPDs
\ Deflection Angle
0.106
86%
84%
78%
29%
0.179
89%
91%
81%
28%
0.3
91%
85%
85%
23%
(c) Theoretical transmission due to loss of reflection for optimized DLPPDs
\ Deflection Angle
0.106
91%
90%
86%
57%
0.179
89%
89%
84%
57%
0.3
88%
88%
84%
57%
Table 4.
Ratio of at Middle of Optimized DTPPDs to at Output Surface of Optimized DTPPDs When DTPPDs Work as Positive Deflectors and Negative Deflectors
Ratio of at Middle of DLPPD to Top of DLPPD
\ Deflection Angle
− Deflector
+ Deflector
0.106\40°
0.10
0.83
0.179\40°
0.03
0.90
0.3\40°
0.08
0.68
0.179\60°
0.03
0.69
Tables (4)
Table 1.
FDTD Simulation Parameters
Properties of Input Light
Wavelength Gaussian beam
FDTD Parameters
Grid resolution
Computation Domain
Total width of grating source layer to computation region grids computation region to NFFF layer
Far-Field Screen
distance between PG and far field screen , angular resolution of far-field screen
Table 2.
(a) Optimized On-Axis Twist Angle for DTPPDs at Different Deflection Angles and Different Birefringence, (b) Optimized Value of nd for DTPPDs at Different Deflection Angles and Different Birefringence, (c) Range of nd for Optimized DTPPDs Where Intrinsic Diffraction Efficiency Is Larger Than 90%, (d) On-Axis Twist Angle Range Where Intrinsic Diffraction Efficiency of DTPPDs Can Be Larger Than 95% by Optimization of Value of nd
(a) Optimized on-axis Twist Angle
\ Deflection Angle
0.106
60
120
250
320
0.179
55
75
160
180
0.3
40
60
85
130
(b) Optimized value of nd ()
\ Deflection Angle
0.106
0.179
0.3
(c) nd range where intrinsic diffraction efficiency for optimized ()
\ Deflection Angle
0.106
0.179
0.3
(d) angle where intrinsic diffraction efficiency can be (°)
We estimate range simply by the other side.
It can have a high efficiency range that is much wider than the range of our simulation.
Due to the precision of our simulation parameters, the maximum efficiency is slightly less than .
Table 3.
(a) Simulation Result of Intrinsic Diffraction Efficiency of Optimized DTPPDs, (b) Device Efficiency of Optimized DTPPDs, (c) Theoretical Transmission Due to Loss of Reflection by Fresnel Equation
(a) Optimized Intrinsic Diffraction Efficiency
\ Deflection Angle
0.106
99.53%
98.44%
98.93%
95.27%
0.179
99.54%
99.29%
99.22%
94.55%
0.3
99.12%
98.90%
99.31%
95.82%
(b) Device Efficiency for optimized DLPPDs
\ Deflection Angle
0.106
86%
84%
78%
29%
0.179
89%
91%
81%
28%
0.3
91%
85%
85%
23%
(c) Theoretical transmission due to loss of reflection for optimized DLPPDs
\ Deflection Angle
0.106
91%
90%
86%
57%
0.179
89%
89%
84%
57%
0.3
88%
88%
84%
57%
Table 4.
Ratio of at Middle of Optimized DTPPDs to at Output Surface of Optimized DTPPDs When DTPPDs Work as Positive Deflectors and Negative Deflectors