Search

Clinical relevance: Currently eye examinations are usually based on autorefraction followed by subjective refraction (SR) with a phoropter. An automated phoropter that can also perform autorefraction may facilitate the optometric workflow. Background: The efficiency and feasibility of an objective autorefraction and correction system are assessed by comparing objective refractive measurements with SR on the same subjects and evaluating the visual acuity (VA) values obtained after the objective refractive measurement and correction. Methods: Objective autorefraction and correction was performed on 41 subjects using an automated binocular phoropter system. The auto-phoropter performs autorefraction by wavefront measurement and corrects the spherical and cylindrical errors with tunable fluidic lenses while the patient looks at a visual display inside the instrument. The instrument outputs are optometric constants of spherical and cylindrical aberrations. After measurement and automated correction of the refractive errors, the VA values were assessed by having the subjects look at an integrated Snellen chart. The objective measurement results were statistically compared with their SR. Results: The correlations between SR and objective autorefraction and correction spherical equivalents (M) were 0.98 (0.97–0.99) and 0.96 (0.93–0.98), the vertical Jackson cross cylinder (J0) were 0.96 (0.92–0.98) and 0.95 (0.91–0.97), and the oblique Jackson cross cylinder (J45) were 0.73 (0.55–0.85) and 0.82 (0.69–0.90), for the right and left eyes, respectively, with the 95% confidence interval (CI) values in parentheses. 89.0% of the 82 eyes had at least 6/7.5 VA. Conclusions: A significant agreement between the SR and objective autorefraction and correction was observed. An all-objective refractive assessment with instantaneous verification may improve the precision of eye prescriptions and possibly reduce the procedure time. [ABSTRACT FROM AUTHOR]

In recent years, there has been a dramatically increasing demand for high-performance narrow-linewidth lasers for optical atomic clock and quantum applications. In this paper, we report on a single-frequency distributed Bragg reflector fiber laser operating at 871 nm that can be used to produce a 435.5 nm narrow-linewidth laser for a Yb+ clock via second-harmonic generation. Linearly polarized single-longitudinal-mode laser output with a power of 6.7 mW and a polarization extinction ratio of 29 dB was obtained by using a 3-cm long 1 wt. % neodymium (Nd3+)-doped phosphate fiber as the gain fiber. [ABSTRACT FROM AUTHOR]

Fluidic lenses have been developed for ophthalmic applications with continuously varying optical powers for second order Zernike modes. Continuously varying corrections for both myopic and hyperopic defocus have been demonstrated over a range of three diopters using a fluidic lens with a circular retaining aperture. Likewise, a six diopter range of astigmatism has been continuously corrected using fluidic lenses with rectangular apertures. Imaging results have been characterized using a model eye. OCIS codes: 080.3630, 170.4460.

In this paper, we present the demonstration of a 10-W level picosecond Yb3+-doped master oscillator and power amplifier at 976 nm in all-fiber configuration. A linear-cavity Yb3+-doped fiber laser mode-locked by a semiconductor-saturable-absorber-mirror was developed as the seed laser with a pulse width of 10.9 ps operating at a repetition rate of 34.1 MHz. The average power of the picosecond mode-locked laser was amplified to 8.1 W by two core-pumped pre-amplifiers and two cladding-pumped power amplifiers. The pulse width of the output mode-locked laser was measured to be 15.6 ps and its pulse energy is 237.5 nJ, corresponding to a peak power of 15.2 kW. The polarization extinction ratio and beam quality (M2) of this 10-watt-level mode-locked laser were measured to be 13 dB and 1.2, respectively. [ABSTRACT FROM AUTHOR]

We show experimental and theoretical results for enhancement of nonlinear transmission (NT) in moderate finesse cavities filled with nonlinear organic materials (NLOM). Our design for enhancement of nonlinear transmission using micro NLOM cavities compared with reference samples of the same material show that single cavities can enhance the nonlinear response by a factor of 10 or greater under high-absorption conditions. Further enhancement can be achieved in multiple-cavity structures. Other advantages of the cavity structures for nonlinear transmission, such as a higher damage threshold and a broader NT band, are also discussed. Our initial experimental results show a threefold reduction in the nonlinear threshold fluence in a single cavity device compared directly to an identical sample without mirrors, in qualitative agreement with our calculations. OCIS codes: 190.4360, 190.4400, 140.3360.

A new method of modeling cladding-pumped Er-Yb Co-doped fiber amplifiers is presented. The method is effective in dealing with the multimode nature of cladding pumped schemes in complicated structures and with the strong linearities in highly Er-Yb-doped fiber amplifiers.

We describe a technique for surface and subsurface micromachining of glass substrates by using tightly focused femtosecond laser pulses at a wavelength of 1660 rim. A salient feature of pulsed laser micromachining is its ability to drill subsurface tunnels into glass substrates. To demonstrate a potential application of this micromachining technique, we fabricate simple microfluidic structures on a glass plate. The use of a cover plate that seals the device by making point-to-point contact with the flat surface of the substrate is necessary to prevent the evaporation of liquids in open channels and chambers. Methods for protecting and sealing the micromachined structures for microfluidic applications are discussed. OCIS codes: 140.7090, 350.3850, 220.4000.

We show that at 1.55-[[micro]meter] wavelength the waveguide birefringence of ion-exchanged channel waveguides in glass can be broadly tuned by a potassium and silver double-ion exchange. Two different potassium and silver double-ion-exchange processes are used to make surface waveguides with negligible waveguide birefringence. This process is crucially important in the manufacture of devices for dense wavelength-division multiplexing systems. The dependence of the waveguide birefringence on the channel width is also reported.

The electron beam-caused alterations of the refractive index and thickness of the amorphous arsenic sulfide (As-S) and arsenic sellenide (As-Se) thin films were studied to determine the suitability of the films in the development of graded index optical components. The technique of thermal evaporation on glass substrates was employed in the preparation of the films. It was observed that the stoichiometric As2S3 structure had the most altered refractive index compared with the As-Se films and that the electron-induced surface contractions were deeper in the As-Se films.

Despite significant advances in silicon photonics, optical packaging and interconnection of photonic integrated circuits constitutes a large portion of the associated manufacturing costs. Optical fibers are the dominant approach to optical interconnection. However, techniques that rely on fibers lack scalability, have low efficiency and show poor misalignment tolerance. Proposed alternative solutions using polymer waveguides have shown improved coupling efficiency, misalignment tolerance and scalability. Here we present the design, simulation and the experimental confirmation of an adiabatic silicon nitride taper to polymer waveguide coupler with only 0.52 dB of TE coupling loss at 1550-nm wavelength, excluding material loss. The coupler demonstrates $\pm 4~\mu \text{m}$ of lateral misalignment tolerance with a 1-dB penalty which, to the best of our knowledge, is the highest reported tolerance for silicon nitride to polymer waveguide coupling. [ABSTRACT FROM AUTHOR]