Phase Change Materials for Photonics - nanoHUB.org

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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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Phase Change Materials for Photonics

ECE 695 Chang Keun Yoon

https://engineering.purdue.edu/ZBML/


http://www.purdue.edu/discoverypark/nanotechnology/

http://www.purdue.edu/

http://www.purdue.edu/discoverypark/




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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









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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









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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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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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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









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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









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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









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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.






Phase Change Materials for Photonics - nanoHUB.org

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