Ziaie Biomedical Microdevices Laboratory Birck Nanotechnology Center 1205 W State St West Lafayette, IN 47907 https://engineering.purdue.edu/ZBML/ 1 Phase Change Materials for Photonics ECE 695 Chang Keun Yoon
Z i a i e B i o m e d i c a l M i c r o d e v i c e s L a b o r a t o r y
B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Phase Change Materials for Photonics
ECE 695 Chang Keun Yoon
Z i a i e B i o m e d i c a l M i c r o d e v i c e s L a b o r a t o r y
B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Contents
Z. Yang et al., Photonics journal, 2015.
• Working principle of PCM in photonics
• Two PCMs in photonic system
• Refractive index and transmittance
• Optical properties of PCMs
• Applications • Writing of reconfigurable photonic
devices in a phase-change film
• Ultra-thin perfect absorber
• Non-volatile memory
Z i a i e B i o m e d i c a l M i c r o d e v i c e s L a b o r a t o r y
B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Working principle of PCM in photonics • Atomic arrangement of different states
in PCM introduces large change in optical and electrical properties.
• Solid-state phase change systems
– Vanadium dioxide (VO2) Electronic transition and structural transition – Chalcogenide (Ge2Sb2Te5) Amorphous and crystalline state transition
• Change of properties in 2 different
states – Dielectric function, – Refractive index, n – Carrier density and electrical conductivity
CD-RW technologies, technical forum, northallegheny.org
Z. Yang et al., Photonics Journal, 2015.
M. Wuttig et al., Nature photonics, 2017
rhombohedral octahedral-like
Z i a i e B i o m e d i c a l M i c r o d e v i c e s L a b o r a t o r y
B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Two recent advanced PMC in Photonics
• VO2 (an oxide system) – Metal to semiconductor
(Monoclinic to tetragonal) transition, vice versa at 70ºC
– Sharp discontinuity in electrical conductivity
M. Wuttig et al., Nature Materials, 2007.
• Ge3Sb2Te6 (Chalcogenide system) – Atomic arrangement in amorphous and
crystalline states
– Some bonds still remain strong bonds: local arrange of atoms
– Forms crystal as before transition
Y. Li et al., Scientific reports, 2013.
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B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Temperature dependent optical properties
Kang et al., Thin solid films, 2012
• Amorphous and crystalline structure grown in different temperatures.
• Crystalline grown Vanadium oxide systems show higher refractive index, n.
• Transmittance in higher temperature show lower transmittance.
• Transmittance of VO2 at 100 ºC (crystalline) is 7.4% less than room temperature (amorphous).
V2O5
VO2
VO2
Amorphous
Crystalline
Crystalline
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W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Optical properties of PCMs
• Increase in refractive index (n), extinction coefficient (k), and reflectance (R) after crystallization.
• Significant changes in bonding introduces difference in optical dielectric constant.
Crystallization
Amorphous
M. Wuttig et al., Nature photonics, 2017
Z i a i e B i o m e d i c a l M i c r o d e v i c e s L a b o r a t o r y
B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Writing of reconfigurable photonic devices in a PCM film • Fresnel zone-plates
• Structural phase changed from amorphous (n= 3.9) to crystalline (n=4.3).
• Optical pulses of different duration, typically consisting of a few tens of 85 fs pulses.
N. I. Zheludev., Nature photonics, 2015
Z i a i e B i o m e d i c a l M i c r o d e v i c e s L a b o r a t o r y
B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Ultra-thin perfect absorber
• Co-existence of phase transition.
• At 343K, the reflectivity drops to ~0.0025 at λ=11.6 µm.
• Hysteresis when temp. switches DC resistance
• n >> k, Total reflection is coherence sum of partial reflection. Phase shift = -
• n ~ k, Absorption resonance exists with thickness of dielectric smaller than λ.
M. A. Kats et al., Applied physics letter, 2012
Z i a i e B i o m e d i c a l M i c r o d e v i c e s L a b o r a t o r y
B i r c k N a n o t e c h n o l o g y C e n t e r 1 2 0 5 W S t a t e S t
W e s t L a f a y e t t e , I N 4 7 9 0 7 h t t p s : / / e n g i n e e r i n g . p u r d u e . e d u / Z B M L /
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Non-volatile memory applications • Large refractive index (~ 2)
change. • High-speed phase transition
10 ~ 100 ns. • Long shelf-life (room temp.). • More than 100,000 cycles.
M. Wuttig et al., Nature Materials, 2007.