The mid-infrared (mid-IR) spectral region contains the characteristic vibrational absorption bands of most molecules as well as two atmospheric transmission windows, and is therefore of critical importance to many biomedical, military, and industrial applications such as spectroscopic sensing, thermal imaging, free-space communications, and infrared countermeasures. Metasurface devices operating in the mid-IR potentially offer significantly reduced size, weight, and cost compared to traditional bulk optics, but they are also challenged with unique material and processing requirements. By combining high-index, broadband transparent dielectric materials with a Huygens metasurface design, we have experimentally realized high-performance metasurface devices with a low-profile, deep sub-wavelength thickness. Based on the platform, we demonstrated single-layer metalenses with focusing efficiencies up to 75% and diffraction-limited performance over a record field of view close to 180 degrees. These meta-optical devices can provide significantly enhanced design flexibility for future infrared optical systems.
The mid-wave infrared (MWIR) is an important band for numerous applications ranging from night vision to biochemical sensing. However, unlike visible or near-infrared (NIR) optical parts, which are economically available off the shelf, MWIR optics are plagued by much higher costs and often inferior performance compared to their visible or NIR counterparts. Optical metasurfaces, artificial materials with subwavelength-scale thicknesses and on-demand electromagnetic responses, provide a promising solution for cost-effective, high-performance infrared optics. Using high-refractive-index (> 5) chalcogenide materials deposited on IR-transparent substrates, we have experimentally demonstrated a MWIR transmissive metasurface device with diffraction-limited focusing and imaging performance and optical efficiency up to 75%. We further show that the metasurface design can accommodate ultra-wide field-of-view and the fabrication method can be extended to conformal integration of metasurface optics on curved surfaces. The projected size, weight and power advantages, coupled with the manufacturing scalability leveraging standard microfabrication technologies, makes the meta-optical devices promising for next-generation MWIR system applications.
In this paper, we proposed highly efficient all-dielectric Huygens’ metasurfaces working at mid-IR frequencies. The meta-atom of the designed Huygens’ metasurface is a cubic dielectric resonator or its variety, which is made from PbTe that possesses a high refractive index of around 5 at mid-IR frequencies. By overlapping spectrally both the magnetic and electric dipole modes of the high-index dielectric resonators, a full phase coverage of 2π and an equal-magnitude transmission could be achieved, which are essential conditions for realizing a metasurface. Two Huygens’ metasurfaces for beam bending are designed with a phase change between two consecutive meta-atoms of π/4 and π/3, respectively. The simulation results agree well with the design theory.
We propose a high-resolution optical time domain reflectometry (OTDR) based on an all-fiber supercontinuum source. The source simply consists of a laser with moderate power and a section of fiber which has a zero dispersion wavelength near the laser’s central wavelength. Spectrum and time domain properties of the source are investigated, showing that the source has great capability in nonlinear optics, such as correlation OTDR. We analyze one of the key factors limiting the operational range of such an OTDR, i.e., sampling time. Finally, we experimentally demonstrate a correlation OTDR with 25km sensing range and 5.3cm spatial resolution, as a verification of theoretical analysis.
A phase-sensitive optical time-domain reflectometry with 175km sensing range is demonstrated using the combination of
co-pumping 2nd-order Raman amplification based on random fiber lasing, counter-pumping 1st-order Raman
amplification, and counter-pumping Brillouin amplification. With elaborate arrangements, each pumping scheme is
responsible for the signal amplification in one particular segment of the all three. To the best of our knowledge, this is
the first time that distributed vibration sensing is performed over such a long distance without inserting repeaters. The
novel hybrid amplification scheme demonstrated in this work can also be incorporated in other fiber-optic sensing
systems for extension of sensing distance.
A long-range (124km) fully distributed fiber-optic vibration sensing system is demonstrated, based on phase-sensitive
optical time-domain reflectometry (Φ-OTDR) with counter-pumping distributed fiber Brillouin amplification (FBA).
FBA significantly enhances the probe pulse signal at the second half of the sensing fiber with less than 10dBm pump
power, and its amplification efficiency is demonstrated to be much higher than 26.9dBm counter-pumping Raman
amplification. As a result, demodulated intrusion signals along the whole sensing range can keep high signal to noise
ratio. The FBA scheme demonstrated in this work can also be incorporated in many other distributed fiber-optic sensing
systems for extension of sensing distance.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.