• 2D broadband beamsteering with large-scale MEMS optical phased array

      Wang, Youmin; Zhou, Guangya; Zhang, Xiaosheng; Kwon, Kyungmok; Blanche, Pierre-A.; Triesault, Nicholas; Yu, Kyoung-sik; Wu, Ming C.; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2019-04-29)
      Optical-phased arrays (OPAs) enable complex beamforming, random-access beam pointing, and simultaneous scan and tracking of multiple targets by controlling the phases of two-dimensional (2D) coherent emitters. So far, no OPA can achieve all desirable features including large 2D arrays, high optical efficiency, wideband operation in wavelengths, fast response time, and large steering angles at the same time. Here, we report on a large-scale 2D OPA with novel microelectro-mechanical-system (MEMS)-actuated phase shifters. Wavelength-independent phase shifts are realized by physically moving a grating element in the lateral direction. The OPA has 160 x 160 independent phase shifters across an aperture of 3.1 mm x 3.2 mm. It has a measured beam divergence of 0.042 degrees x 0.031 degrees, a field of view (FOV) of 6.6 degrees x 4.4 degrees, and a response time of 5.7 mu s. It is capable of providing about 25,600 rapidly steerable spots within its FOV. The grating phase shifters are optimized for the near-infrared telecom wavelength bands from 1200 to 1700 nm with 85% optical efficiency. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • 3D imaging of gems and minerals by multiphoton microscopy

      Cromey, Benjamin; Knox, Ryan J.; Kieu, Khanh; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2019-02-01)
      Many optical approaches have been used to examine the composition and structure of gemstones, both recently and throughout history. The nonlinear optical behavior of different gemstones has not been investigated, and the higher order terms to the refractive index represent an unused tool for qualifying and examining a stone. We have used a multiphoton microscope to examine the nonlinear optical properties of 36 different gemstones and demonstrate that it is a useful tool for imaging them three-dimensionally up to the millimeter scale below the sample surface. The polarization dependence of second harmonic generation signals was used to examine the crystal orientations inside the minerals. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • 6.5  m telescope for multi-object spectroscopy over a 3° field of view

      Eads, Ryker; Angel, Roger; Univ Arizona, Wyant Coll Opt Sci; Univ Arizona, Steward Observ (OPTICAL SOC AMER, 2020-08-01)
      Multi-object spectroscopy via independently positioned optical fibers is of growing importance in many research areas in astronomy. Currently the most powerful instrument of this type is the Dark Energy Spectroscopic Instrument (DESI), now being commissioned at the 3.8 m Mayall telescope. It has a 3.2° field of view where spectra of 5000 different objects may be recorded simultaneously. Here we present an optical design for a two-mirror 6.5 m telescope with 3.0° field of view, for an etendue 2.6 times larger than for DESI. The images are at f/3.7 for fiber matching, and -averaged over the field and elevations down to 40°-have a diameter of 0.53 arcsec for 80% encircled energy. We outline methods capable of polishing and testing the 1.56 m diameter gull-wing lens of the wide field corrector. If a 2 m diameter lens could be made, the same design could be scaled up to an 8.4 m primary for a 4.3-fold etendue advantage.
    • Accurate and fast two-step phase shifting algorithm based on principle component analysis and Lissajous ellipse fitting with random phase shift and no pre-filtering

      Zhang, Yu; Tian, Xiaobo; Liang, Rongguang; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2019-07-05)
      To achieve high measurement accuracy with less computational time-in-phase shifting interferometry, a random phase-shifting algorithm based on principal component analysis and Lissajous ellipse fitting (PCA& LEF) is proposed. It doesn't need pre-filtering and can obtain relatively accurate phase distribution with only two phase shifted interferograms and less computational time and is suitable for different background intensity, modulation amplitude distributions and noises. Moreover, it can obtain absolutely accurate result when the background intensity and modulation amplitude are perfect and can partly suppress the effect of imperfect background intensity and modulation amplitude. Last but not least, it removes the restriction that PCA needs more than three interferograms with welldistributed phase shifts to subtract relatively accurate mean. The simulations and experiments verify the correctness and feasibility of PCA& LEF. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • Accurate calibration of geometrical error in reflective surface testing based on reverse Hartmann test

      Wang, Daodang; Gong, Zhidong; Xu, Ping; Wang, Chao; Liang, Rongguang; Kong, Ming; Zhao, Jun; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2018-04-02)
      The deflectometry provides a powerful metrological technique enabling the high-precision testing of reflective surfaces with high dynamic range, such as aspheric and freeform surfaces. In the fringe-illumination deflectometry based on reverse-Hartmann-test configuration, the calibration of system geometry is required to achieve "null" testing. However, the system miscalibration can introduce a significant systematic error in the testing results. A general double-step calibration method, which is based on the low-order Zernike aberration optimization and high-order aberration separation, is proposed to separate and eliminate the geometrical error due to system miscalibration. Both the numerical simulation and experiments have been performed to validate the feasibility of the proposed calibration method. The proposed method provides a general way for the accurate calibration of system geometrical error, avoids the over-correction and is feasible for the testing of various complex freeform surfaces. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • Advanced GF(3^2) nonbinary LDPC coded modulation with non-uniform 9-QAM outperforming star 8-QAM

      Liu, Tao; Lin, Changyu; Djordjevic, Ivan B.; Univ Arizona, Dept Elect & Comp Engn (OPTICAL SOC AMER, 2016-06-14)
      In this paper, we first describe a 9-symbol non-uniform signaling scheme based on Huffman code, in which different symbols are transmitted with different probabilities. By using the Huffman procedure, prefix code is designed to approach the optimal performance. Then, we introduce an algorithm to determine the optimal signal constellation sets for our proposed non-uniform scheme with the criterion of maximizing constellation figure of merit (CFM). The proposed nonuniform polarization multiplexed signaling 9-QAM scheme has the same spectral efficiency as the conventional 8-QAM. Additionally, we propose a specially designed GF(32) nonbinary quasi-cyclic LDPC code for the coded modulation system based on the 9-QAM non-uniform scheme. Further, we study the efficiency of our proposed non-uniform 9-QAM, combined with nonbinary LDPC coding, and demonstrate by Monte Carlo simulation that the proposed GF(23) nonbinary LDPC coded 9-QAM scheme outperforms nonbinary LDPC coded uniform 8-QAM by at least 0.8dB. (C) 2016 Optical Society of America
    • All-fiber high-power 1700 nm femtosecond laser based on optical parametric chirped-pulse amplification

      Qin, Yukun; Batjargal, Orkhongua; Cromey, Benjamin; Kieu, Khanh; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2020-01-15)
      We present the design and construction of an all-fiber high-power optical parametric chirped-pulse amplifier working at 1700 nm, an important wavelength for bio-photonics and medical treatments. The laser delivers 1.42 W of output average power at 1700 nm, which corresponds to similar to 40 nJ pulse energy. The pulse can be de-chirped with a conventional grating pair compressor to similar to 450 fs. Furthermore, the laser has a stable performance with relative intensity noise typically below the -130 dBc/Hz level for the idler pulses at 1700 nm from 10kHz to 16.95 MHz, half of the laser repetition rate f/2. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • All-fiber polarization-maintaining mode-locked laser operated at 980 nm

      Aleshkina, Svetlana S; Fedotov, Andrei; Korobko, Dmitrii; Stoliarov, Dmitrii; Lipatov, Denis S; Velmiskin, Vladimir V; Temyanko, Valery L; Kotov, Leonid V; Gumenyuk, Regina; Likhachev, Mikhail E; et al. (OPTICAL SOC AMER, 2020-04-15)
      For the first time, to the best of our knowledge, we present an all-fiber polarization-maintaining passively mode-locked picosecond laser operated at 980 nm. The laser cavity had a ring configuration with a semiconductor saturable absorber mirror as a mode-locking element. As an active medium, we used a specially designed cladding-pumped . Yb-doped fiber with reduced cladding-to-core diameter ratio. The laser was self-starting and operated in the net cavity normal dispersion regime, where a spectral profile of the gain medium acted as a filter element. By intracavity spectral filtering, we achieved about 40 dB dominance of the signal wavelength at 980 nm over 1 mu m emission in a highly stable picosecond pulsed regime. The corresponding simulation was performed to extend the knowledge about laser operation. (C) 2020 Optical Society of America
    • All-reflective multiphoton microscope

      Amirsolaimani, Babak; Cromey, Benjamin; Peyghambarian, N.; Kieu, Khanh; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2017-09-15)
      We present the design, construction, and characterization of a multiphoton microscope that uses reflective elements for beam shaping and steering. This compact all reflective design removes the adverse effects of dispersion on laser pulse broadening as well as chromatic aberration in the focusing of broadband and multicolored laser sources. The design of this system is discussed in detail, including aberrations analysis via ray-tracing simulation and opto-mechanical design. The resolution of this mirror based all-reflective microscope is characterized using fluorescent microbeads. The performance of the system at multiple wavelengths is investigated along with some potential multiphoton imaging and writing applications. (C) 2017 Optical Society of America
    • Analysis of spurious diffraction orders of computer-generated hologram in symmetric aspheric metrology

      He, Yiwei; Hou, Xi; Wu, Fan; Ma, Xinxue; Liang, Rongguang; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2017-08-15)
      Computer-generated hologram (CGH) has been widely used as a wavefront compensator in symmetric aspheric metrology. As a diffractive element, it generates different diffraction orders, but only the 1st-order diffraction is used to test aspheric surface. The light from spurious diffraction orders (SDO) will produce many high-frequency fringes in interferogram and reduce measurement accuracy. In this paper, we regard the CGH null system as an imaging system and develop an aberration model in Seidel formalism to analyze the SDO. This model has the advantage to address the difference between the SDO (k(1), k(2)) and (k(2), k(1)). We consider the effect of the pupil distortion so that our model can analyze the SDO with a large pupil distortion. We derive the condition to ensure the 2nd-order and 4th-order aberrations have the same sign and calculate the minimum defocused distance (power carrier frequency) of CGH. According to the marginal-ray heights (h(1) and h(3)) on the CGH in the first and second passes, we determine the condition that the SDO covers the whole CGH in the second pass. We analyze the SDO of 4 CGH designs and compare the results from our aberration model with these from real ray trace. These results validate that our aberration model is feasible whether the aspheric part is convex or concave and whether CGH is inside or outside the focus of the transmission sphere. (C) 2017 Optical Society of America
    • Analysis of the focusing crosstalk effects of broadband all-dielectric planar metasurface microlens arrays for ultra-compact optical device applications

      Özdemir, Aytekin; Yılmaz, Nazmi; Alboon, Shadi A.; Takashima, Yuzuru; Kurt, Hamza; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2018-10-15)
      Microlens arrays have been widely used for different optoelectronic applications. The demand for compact optical devices necessitates the deployment of even smaller microlens arrays; however, as the spacing between individual lenses reduces and the lens diameter approaches the length scale of the incident wavelength of light, diffraction starts playing a critical role and produces a significant impact on the final focusing properties of the optical field. In this paper, we analyze the focusing characteristics of all-dielectric ultra-compact metasurface lens arrays for efficient optical device applications, constructed by kinds of broadband planar lenses composed of subwavelength nano-scatterers. By using the 3D finite-difference time-domain (FDTD) method, focusing and diffraction-based crosstalk effects caused by the changing physical spacing between adjacent metalenses, the diameter of microlenses, the operating wavelength, and the army size are rigorously investigated. Analysis of the achieved results show that a larger spacing, a larger lens size, and a shorter wavelength can lead to a weaker focusing crosstalk effect. Moreover, the crosstalk effect does not have a significant dependence on the array's overall size. This research study may provide an important technological reference to designing an array of all-dielectric planar metasurface lenses with a well-controlled focusing performance and may pave the way further toward the application of metasurface lens arrays in compact optical sensing, coupling, and detecting system designs. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • Angular and spatial light modulation by single digital micromirror device for multi-image output and nearly-doubled étendue

      Hellman, Brandon; Takashima, Yuzuru; Univ Arizona (OPTICAL SOC AMER, 2019-07-16)
      The "Angular Spatial Light Modulator" (ASLM) achieves simultaneous angular and spatial light modulation at a plane by combining Digital Micromirror Device (DMD) based programmable blazed grating beam steering and binary pattern sequencing. The ASLM system multiplies the number of effective output pixels of the DMD for increased spatial and/or angular degrees of freedom, and nearly-doubles the etendue output of the DMD. We implement multiple illumination and projection schemes to demonstrate ASLM-based extended FOV display, light-field projection, and multi-view display. We also implement time-multiplexed pupil segmented illumination to extend the pattern steering to two dimensions. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • Athermal silicon optical add-drop multiplexers based on thermo-optic coefficient tuning of sol-gel material

      Namnabat, Soha; Kim, Kyung-Jo; Jones, Adam; Himmelhuber, Roland; DeRose, Christopher T.; Trotter, Douglas C.; Starbuck, Andrew L.; Pomerene, Andrew; Lentine, Anthony L.; Norwood, Robert A.; et al. (OPTICAL SOC AMER, 2017-08-25)
      Silicon photonics has gained interest for its potential to provide higher efficiency, bandwidth and reduced power consumption compared to electrical interconnects in datacenters and high performance computing environments. However, it is well known that silicon photonic devices suffer from temperature fluctuations due to silicon's high thermo-optic coefficient and therefore, temperature control in many applications is required. Here we present an athermal optical add-drop multiplexer fabricated from ring resonators. We used a sol-gel inorganic-organic hybrid material as an alternative to previously used materials such as polymers and titanium dioxide. In this work we studied the thermal curing parameters of the sol-gel and their effect on thermal wavelength shift of the rings. With this method, we were able to demonstrate a thermal shift down to -6.8 pm/% for transverse electric (TE) polarization in ring resonators with waveguide widths of 325 nm when the sol-gel was cured at 130 % for 10.5 hours. We also achieved thermal shifts below 1 pm/% for transverse magnetic (TM) polarization in the C band under different curing conditions. Curing time compared to curing temperature shows to be the most important factor to control sol-gel's thermo-optic value in order to obtain an athermal device in a wide temperature range. (C) 2017 Optical Society of America
    • Augmented design and analysis of computer experiments: a novel tolerance embedded global optimization approach applied to SWIR hyperspectral illumination design

      Keresztes, Janos C.; John Koshel, R.; D’huys, Karlien; De Ketelaere, Bart; Audenaert, Jan; Goos, Peter; Saeys, Wouter; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2016-12-12)
      A novel meta-heuristic approach for minimizing nonlinear constrained problems is proposed, which offers tolerance information during the search for the global optimum. The method is based on the concept of design and analysis of computer experiments combined with a novel two phase design augmentation (DACEDA), which models the entire merit space using a Gaussian process, with iteratively increased resolution around the optimum. The algorithm is introduced through a series of cases studies with increasing complexity for optimizing uniformity of a short-wave infrared (SWIR) hyperspectral imaging (HSI) illumination system (IS). The method is first demonstrated for a two-dimensional problem consisting of the positioning of analytical isotropic point sources. The method is further applied to two-dimensional (2D) and five-dimensional (5D) SWIR HSI IS versions using close-and far-field measured source models applied within the non-sequential ray-tracing software FRED, including inherent stochastic noise. The proposed method is compared to other heuristic approaches such as simplex and simulated annealing (SA). It is shown that DACEDA converges towards a minimum with 1 % improvement compared to simplex and SA, and more importantly requiring only half the number of simulations. Finally, a concurrent tolerance analysis is done within DACEDA for to the five-dimensional case such that further simulations are not required. (C) 2016 Optical Society of America
    • Bio-inspired imager improves sensitivity in near-infrared fluorescence image-guided surgery

      Garcia, Missael; Edmiston, Christopher; York, Timothy; Marinov, Radoslav; Mondal, Suman; Zhu, Nan; Sudlow, Gail P.; Akers, Walter J.; Margenthaler, Julie; Achilefu, Samuel; et al. (OPTICAL SOC AMER, 2018-04-20)
      Image-guided surgery can enhance cancer treatment by decreasing, and ideally eliminating, positive tumor margins and iatrogenic damage to healthy tissue. Current state-of-the-art near-infrared fluorescence imaging systems are bulky and costly, lack sensitivity under surgical illumination, and lack co-registration accuracy between multimodal images. As a result, an overwhelming majority of physicians still rely on their unaided eyes and palpation as the primary sensing modalities for distinguishing cancerous from healthy tissue. Here we introduce an innovative design, comprising an artificial multispectral sensor inspired by the Morpho butterfly's compound eye, which can significantly improve image-guided surgery. By monolithically integrating spectral tapetal filters with photodetectors, we have realized a single-chip multispectral imager with 1000 x higher sensitivity and 7 x better spatial co-registration accuracy compared to clinical imaging systems in current use. Preclinical and clinical data demonstrate that this technology seamlessly integrates into the surgical workflow while providing surgeons with real-time information on the location of cancerous tissue and sentinel lymph nodes. Due to its low manufacturing cost, our bio-inspired sensor will provide resource-limited hospitals with much-needed technology to enable more accurate value-based health care. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • Bloch oscillations of multidimensional dark soliton wave packets and light bullets

      Driben, Rodislav; Ma, Xuekai; Schumacher, Stefan; Meier, Torsten; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2019-03-15)
      The robust propagation of dark solitonic waves featuring Bloch oscillations (BOs) in media with a Kerr nonlinearity is demonstrated. The models considered have a discrete refractive index gradient in one dimension and are continuous in the orthogonal direction or directions. Such systems can be realized in photonic settings, where temporal dispersion of a normal type is able to support dark solitons. The demonstrated effects may also appear in the dynamics of Bose-Einstein condensates (BECs), where dark solitons appear due to the joint action of diffraction and a self-defocusing nonlinearity. Furthermore, our analysis shows that a periodic variation of the refractive index gradient in the propagation direction allows us to realize the spatial analog of dynamical localization. In addition, we demonstrate that dark solitons serve as excellent supporters for light bullets of a peculiar dark-bright type that can also feature robust BOs.
    • Broadband extended source imaging Mueller-matrix polarimeter

      López-Téllez, Juan Manuel; Chipman, Russell A.; Li, Lisa W.; McEldowney, Scott C.; Smith, Matthew H.; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2019-04-01)
      An imaging Mueller matrix polarimeter, named the red–green–blue (RGB)950, takes images of medium-sized (tens of centimeters) objects by using a very bright source, large polarization state generator, and high-quality camera. Its broadband extended light source switches between red, green, blue, and near-infrared light to allow taking polarimetric images for comparison with RGB camera images. The large diffuse source makes shadow transitions gradual and spreads out the specular reflected spot into a larger less conspicuous area.
    • Broadband wavelength converters with flattop responses based on cascaded second-harmonic generation and difference frequency generation in Bessel-chirped gratings

      Liu, Tao; Djordjevic, Ivan B.; Song, Zekun; Chen, Ying; Zhang, Rongxiang; Zhang, Ke; Zhao, Wei; Li, Baogang; Univ Arizona, Dept Elect & Comp Engn (OPTICAL SOC AMER, 2016-05-10)
      We investigate ultra-broadband wavelength converters based on cascaded second-harmonic generation and difference frequency generation using Bessel-chirped gratings (BCGs) in lithium niobate waveguides, and compare them to the ones using uniform grating and segmented grating, respectively. For the same length and power, the BCGs show broader bandwidth than the other two types of grating. The ripple of the matching response is very small as well. Analysis also shows that almost the same conversion bandwidth and maximum conversion efficiency with tolerant response flatness can be achieved when the manufacturing tolerance of the waveguide length is smaller than 0.1 cm.
    • Capacity achieving nonbinary LDPC coded non-uniform shaping modulation for adaptive optical communications.

      Lin, Changyu; Zou, Ding; Liu, Tao; Djordjevic, Ivan B; Univ Arizona, Dept Elect & Comp Engn (OPTICAL SOC AMER, 2016-08-08)
      A mutual information inspired nonbinary coded modulation design with non-uniform shaping is proposed. Instead of traditional power of two signal constellation sizes, we design 5-QAM, 7-QAM and 9-QAM constellations, which can be used in adaptive optical networks. The non-uniform shaping and LDPC code rate are jointly considered in the design, which results in a better performance scheme for the same SNR values. The matched nonbinary (NB) LDPC code is used for this scheme, which further improves the coding gain and the overall performance. We analyze both coding performance and system SNR performance. We show that the proposed NB LDPC-coded 9-QAM has more than 2dB gain in symbol SNR compared to traditional LDPC-coded star-8-QAM. On the other hand, the proposed NB LDPC-coded 5-QAM and 7-QAM have even better performance than LDPC-coded QPSK.
    • Catadioptric freeform optical system design for LED off-axis road illumination applications

      Zhu, Zhengbo; Ma, Donglin; Hu, Qiaomu; Tang, Yongqian; Liang, Rongguang; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2017-12-04)
      The aim of this paper is to develop a new composite structure of catadioptric optical system containing both freeform refractive surface and freeform total internal reflective (TIR) surface for LED road illumination applications. The role of freeform refractive part is to generate the shifted general rectangular illumination pattern to optimally match the shape of the road surface. The application of TIR mechanism is aimed to control the stray light in the sidewalk direction of the road luminaire and maximize the efficient energy efficiency. In this paper, we use the "double pole" ray mapping technique to design the refractive optical surface and the theta-phi coordinate ray mapping technique to derive the freeform TIR surface. The simulation shows that the novel catadioptric design has relatively high collection efficiency, thus high average illuminance level inside the effective illumination area. This lens also has good control of stray light on the backside of the road luminaire. (c) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement