More Like this

1. Large-area, high-numerical-aperture multi-level diffractive lens via inverse design: reply

   https://doi.org/10.1364/OPTICA.427037  

   Meem, Monjurul ; Banerji, Sourangsu ; Majumder, Apratim ; Sensale-Rodriguez, Berardi ; Menon, Rajesh ( July 2021 , Optica)

   We proposed the use of relative encircled power as a measure of focusing efficiency [Optica7,252(2020)OPTIC82334-253610.1364/OPTICA.388697]. The comment [Optica8,1009(2021)OPTIC82334-253610.1364/OPTICA.416017] has raised useful questions, which we address briefly here and provide some clarifications.

    

   more » « less
2. Ultralow-threshold thin-film lithium niobate optical parametric oscillator: erratum

   https://doi.org/10.1364/OPTICA.432006  

   Lu, Juanjuan ; Sayem, Ayed Al ; Gong, Zheng ; Surya, Joshua B. ; Zou, Chang-Ling ; Tang, Hong X. ( June 2021 , Optica)

   This erratum corrects a typographic error that appears in Table 1 of our earlier paper [Optica8,539(2021)OPTIC82334-253610.1364/OPTICA.418984].

    

   more » « less
3. Engineering optomechanically induced transparency by coupling a qubit to a spinning resonator

   https://doi.org/10.1364/JOSAB.478320  

   Burns, Jessica ; Root, Owen ; Jing, Hui ; Mirza, Imran M. ( April 2023 , Journal of the Optical Society of America B)

   We theoretically study the spectral properties of a pump–probe driven hybrid spinning optomechanical ring resonator optically coupled with a two-level quantum emitter (QE or qubit). Recently, we have shown [Opt. Express27,25515(2019)OPEXFF1094-408710.1364/OE.27.025515] that in the absence of the emitter, the coupled cavity version of this setup is not only capable of non-reciprocal light propagation but can also exhibit slow and fast light propagation. In this work, we investigate in what ways the presence of a single QE coupled with the optical whispering gallery modes of a spinning optomechanical resonator can alter the probe light non-reciprocity. Under the weak-excitation assumption and mean-field approximation, we find that the interplay between the rotational/spinning Sagnac effect and qubit coupling can lead to enhancement of both the optomechanically induced transparency peak value and the width of the transparency window due to the opening of a qubit-assisted backreflection channel. However, compared to the no-qubit case, we notice that such enhancement comes at the cost of degrading the group delay in probe light transmission by a factor of 1/2 for clockwise rotary directions. The target applications of these results can be in the areas of quantum circuitry and in non-reciprocal quantum communication protocols where QEs are a key component.

    

   more » « less
4. Adaptive optics approach to surface-enhanced Raman scattering

   https://doi.org/10.1364/OL.394548  

   Shutova, Mariia ; Sinyukov, Alexander M. ; Birmingham, Blake ; Zhang, Zhenrong ; Sokolov, Alexei V. ( June 2020 , Optics Letters)

   Surface-enhanced Raman scattering (SERS) spectroscopy is a popular technique for detecting chemicals in small quantities. Rough metallic surfaces with nanofeatures are some of the most widespread and commercially successful substrates for efficient SERS measurements. A rough metallic surface creates a high-density random distribution of so-called “hot spots” with local optical field enhancement causing Raman signal to increase. In this Letter, we revisit the classic SERS experiment [Surf. Sci.158,229(1985)SUSCAS0039-602810.1016/0039-6028(85)90297-3] with rough metallic surfaces covered by a thin layer of copper phthalocyanine molecules. As a modification to the classic configuration, we apply an adaptive wavefront correction of a laser beam profile. As a result, we demonstrate an increase in brightness of local SERS hot spots and redistribution of Raman signal over the substrate area. We hypothesize that the improvement is due to optimal coupling of the shaped laser beam to the random plasmonic nanoantenna configurations. We show that the proposed adaptive-SERS modification is independent of the exact structure of the surface roughness and topography, works with many rough surfaces, and gives brighter Raman hot spots in comparison with conventional SERS measurements. We prove that the adaptive SERS is a powerful instrument for improving SERS sensitivity.

    

   more » « less
5. Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading. Part II: finite-difference algorithm and double-layer antireflection coatings

   https://doi.org/10.1364/AO.474920  

   Ahmad, Faiz ; Civiletti, Benjamin J. ; Monk, Peter B. ; Lakhtakia, Akhlesh ( November 2022 , Applied Optics)

   In Part I [Appl. Opt.58,6067(2019)APOPAI003-693510.1364/AO.58.006067], we used a coupled optoelectronic model to optimize a thin-film${\mathrm{C}\mathrm{u}\mathrm{I}\mathrm{n}}_{1-<\#comment/>\mathrm{\xi <\#comment/>}}{\mathrm{G}\mathrm{a}}_{\mathrm{\xi <\#comment/>}}{\mathrm{S}\mathrm{e}}_2$(CIGS) solar cell with a graded-bandgap photon-absorbing layer and a periodically corrugated backreflector. The increase in efficiency due to the periodic corrugation was found to be tiny and that, too, only for very thin CIGS layers. Also, it was predicted that linear bandgap-grading enhances the efficiency of the CIGS solar cells. However, a significant improvement in solar cell efficiency was found using a nonlinearly (sinusoidally) graded-bandgap CIGS photon-absorbing layer. The optoelectronic model comprised two submodels: optical and electrical. The electrical submodel applied the hybridizable discontinuous Galerkin (HDG) scheme directly to equations for the drift and diffusion of charge carriers. As our HDG scheme sometimes fails due to negative carrier densities arising during the solution process, we devised a new, to the best of our knowledge, computational scheme using the finite-difference method, which also reduces the overall computational cost of optimization. An unfortunate normalization error in the electrical submodel in Part I came to light. This normalization error did not change the overall conclusions reported in Part I; however, some specifics did change. The new algorithm for the electrical submodel is reported here along with updated numerical results. We re-optimized the solar cells containing a CIGS photon-absorbing layer with either (i) a homogeneous bandgap, (ii) a linearly graded bandgap, or (iii) a nonlinearly graded bandgap. Considering the meager increase in efficiency with the periodic corrugation and additional complexity in the fabrication process, we opted for a flat backreflector. The new algorithm is significantly faster than the previous algorithm. Our new results confirm efficiency enhancement of 84% (resp. 63%) when the thickness of the CIGS layer is 600 nm (resp. 2200 nm), similarly to Part I. A hundredfold concentration of sunlight can increase the efficiency by an additional 27%. Finally, the currently used 110-nm-thick layer of${\mathrm{M}\mathrm{g}\mathrm{F}}_2$performs almost as well as optimal single- and double-layer antireflection coatings.

    

   more » « less