We present the optical and structural characterization of films of
Optical coatings formed from amorphous oxide thin films have many applications in precision measurements. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo use coatings of
- NSF-PAR ID:
- 10217577
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Journal of the Optical Society of America A
- Volume:
- 38
- Issue:
- 4
- ISSN:
- 1084-7529; JOAOD6
- Page Range / eLocation ID:
- Article No. 534
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
, , and doped with a cation ratio around 0.1 grown by reactive sputtering. The addition of as a dopant induces the formation of tantalum suboxide due to the “oxygen getter” property of scandium. The presence of tantalum suboxide greatly affects the optical properties of the coating, resulting in higher absorption loss at . The refractive index and optical band gap of the mixed film do not correspond to those of a mixture of and , given the profound structural modifications induced by the dopant. -
Mechanical loss of dielectric mirror coatings sets fundamental limits for both gravitational wave detectors and cavity-stabilized optical local oscillators for atomic clocks. Two approaches are used to determine the mechanical loss: ringdown measurements of the coating quality factor and direct measurement of the coating thermal noise. Here we report a systematic study of the mirror thermal noise at 4, 16, 124, and 300 K by operating reference cavities at these temperatures. The directly measured thermal noise is used to extract the mechanical loss for
coatings, which are compared with previously reported values. -
The mid-IR spectroscopic properties of
doped low-phonon and crystals grown by the Bridgman technique have been investigated. Using optical excitations at and , both crystals exhibited IR emissions at , , , and at room temperature. The mid-IR emission at 4.5 µm, originating from the transition, showed a long emission lifetime of for doped , whereas doped exhibited a shorter lifetime of . The measured emission lifetimes of the state were nearly independent of the temperature, indicating a negligibly small nonradiative decay rate through multiphonon relaxation, as predicted by the energy-gap law for low-maximum-phonon energy hosts. The room temperature stimulated emission cross sections for the transition in doped and were determined to be and , respectively. The results of Judd–Ofelt analysis are presented and discussed. -
Electro-optic quantum coherent interfaces map the amplitude and phase of a quantum signal directly to the phase or intensity of a probe beam. At terahertz frequencies, a fundamental challenge is not only to sense such weak signals (due to a weak coupling with a probe in the near-infrared) but also to resolve them in the time domain. Cavity confinement of both light fields can increase the interaction and achieve strong coupling. Using this approach, current realizations are limited to low microwave frequencies. Alternatively, in bulk crystals, electro-optic sampling was shown to reach quantum-level sensitivity of terahertz waves. Yet, the coupling strength was extremely weak. Here, we propose an on-chip architecture that concomitantly provides subcycle temporal resolution and an extreme sensitivity to sense terahertz intracavity fields below 20 V/m. We use guided femtosecond pulses in the near-infrared and a confinement of the terahertz wave to a volume of
in combination with ultraperformant organic molecules ( ) and accomplish a record-high single-photon electro-optic coupling rate of , 10,000 times higher than in recent reports of sensing vacuum field fluctuations in bulk media. Via homodyne detection implemented directly on chip, the interaction results into an intensity modulation of the femtosecond pulses. The single-photon cooperativity is , and the multiphoton cooperativity is at room temperature. We show dynamic range in intensity at 500 ms integration under irradiation with a weak coherent terahertz field. Similar devices could be employed in future measurements of quantum states in the terahertz at the standard quantum limit, or for entanglement of subsystems on subcycle temporal scales, such as terahertz and near-infrared quantum bits. -
Amorphous tantala (
) thin films were deposited by reactive ion beam sputtering with simultaneous low energy assist or bombardment. Under the conditions of the experiment, the as-deposited thin films are amorphous and stoichiometric. The refractive index and optical band gap of thin films remain unchanged by ion bombardment. Around 20% improvement in room temperature mechanical loss and 60% decrease in absorption loss are found in samples bombarded with 100-eV . A detrimental influence from low energy bombardment on absorption loss and mechanical loss is observed. Low energy bombardment removes excess oxygen point defects, while bombardment introduces defects into the tantala films.