skip to main content


Title: Independent measurement of phase and amplitude modulation in phase change material-based devices

For active beam manipulation devices, such as those based on liquid crystals, phase-change materials, or electro-optic materials, measuring accumulated phase of the light passing through a layer of the material is imperative to understand the functionality of the overall device. In this work we discuss a way of measuring the phase accumulation through a switched layer of Ge2Sb2Te5, which is seeing rapid use as means to high speed dynamic reconfiguration of free space light. Utilizing an interferometer in the switching setup and modulating the phase of one arm, the intensity of a probe beam can be captured and phase data pulled from it. Simulations were used to discover the connection between the intensity modulations and the phase information. The technique was tested experimentally and it was found that within error, the measurement was robust and repeatable.

 
more » « less
NSF-PAR ID:
10369490
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
Optical Society of America
Date Published:
Journal Name:
Optical Materials Express
Volume:
12
Issue:
7
ISSN:
2159-3930
Page Range / eLocation ID:
Article No. 2899
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Phase-change materials (PCMs) offer a compelling platform for active metaoptics, owing to their large index contrast and fast yet stable phase transition attributes. Despite recent advances in phase-change metasurfaces, a fully integrable solution that combines pronounced tuning measures, i.e., efficiency, dynamic range, speed, and power consumption, is still elusive. Here, we demonstrate an in situ electrically driven tunable metasurface by harnessing the full potential of a PCM alloy, Ge2Sb2Te5(GST), to realize non-volatile, reversible, multilevel, fast, and remarkable optical modulation in the near-infrared spectral range. Such a reprogrammable platform presents a record eleven-fold change in the reflectance (absolute reflectance contrast reaching 80%), unprecedented quasi-continuous spectral tuning over 250 nm, and switching speed that can potentially reach a few kHz. Our scalable heterostructure architecture capitalizes on the integration of a robust resistive microheater decoupled from an optically smart metasurface enabling good modal overlap with an ultrathin layer of the largest index contrast PCM to sustain high scattering efficiency even after several reversible phase transitions. We further experimentally demonstrate an electrically reconfigurable phase-change gradient metasurface capable of steering an incident light beam into different diffraction orders. This work represents a critical advance towards the development of fully integrable dynamic metasurfaces and their potential for beamforming applications.

     
    more » « less
  2. The objective of this Opinion is to stimulate new research into materials that can meet the needs of tomorrow’s programmable photonics components. Herein, we argue that the inherent property portfolios of the common telluride phase change materials, which have been successfully applied in data storage technologies, are unsuitable for most emerging programmable photonics applications. We believe that newer PCMs with wider bandgaps, such as Sb2S3, Sb2Se3, and Ge2Sb2Se4Te (GSST), can be optimized to meet the demands of holographic displays, optical neural network memories, and beam steering devices.

     
    more » « less
  3. Abstract

    The primary mechanism of optical memoristive devices relies on phase transitions between amorphous and crystalline states. The slow or energy‐hungry amorphous–crystalline transitions in optical phase‐change materials are detrimental to the scalability and performance of devices. Leveraging an integrated photonic platform, nonvolatile and reversible switching between two layered structures of indium selenide (In2Se3) triggered by a single nanosecond pulse is demonstrated. The high‐resolution pair distribution function reveals the detailed atomistic transition pathways between the layered structures. With interlayer “shear glide” and isosymmetric phase transition, switching between the α‐ and β‐structural states contains low re‐configurational entropy, allowing reversible switching between layered structures. Broadband refractive index contrast, optical transparency, and volumetric effect in the crystalline–crystalline phase transition are experimentally characterized in molecular‐beam‐epitaxy‐grown thin films and compared to ab initio calculations. The nonlinear resonator transmission spectra measure of incremental linear loss rate of 3.3 GHz, introduced by a 1.5 µm‐long In2Se3‐covered layer, resulted from the combinations of material absorption and scattering.

     
    more » « less
  4. A majority of ultracold atom experiments utilize resonant absorption imaging techniques to obtain the atomic density. To make well-controlled quantitative measurements, the optical intensity of the probe beam must be precisely calibrated in units of the atomic saturation intensityIsat. In quantum gas experiments, the atomic sample is enclosed in an ultra-high vacuum system that introduces loss and limits optical access; this precludes a direct determination of the intensity. Here, we use quantum coherence to create a robust technique for measuring the probe beam intensity in units ofIsatvia Ramsey interferometry. Our technique characterizes the ac Stark shift of the atomic levels due to an off-resonant probe beam. Furthermore, this technique gives access to the spatial variation of the probe intensity at the location of the atomic cloud. By directly measuring the probe intensity just before the imaging sensor our method in addition yields a direct calibration of imaging system losses as well as the quantum efficiency of the sensor.

     
    more » « less
  5. Abstract

    The layered semiconductor In2Se3has a low temperature crystalline–crystalline (α → β) phase transformation with distinct electrical properties that make it a promising candidate for phase change memory. Here, using scanning tunneling microscopy, correlative in situ micro‐Raman, and electrical measurements, it is shown that the β phase can persist in bulk crystals at room temperature in non‐oxidative environments. Of particular note, the stability of β phase crystals in ambient conditions under encapsulation of graphene and similar passivation layers, is reported for the first time. The strategy of encapsulation to ensure the persistence of β phase overlaps with efforts to passivate switching materials. It is further demonstrated that degradation from the elevated temperatures required for the phase change is slowed through examination of Raman signatures. These results demonstrate an alternative method of phase manipulation with a new stabilization of β‐In2Se3in ambient conditions potentially extendable to other polymorphic materials, and the importance of passivation in In2Se3memory devices.

     
    more » « less