Search results for "Optical power"
showing 10 items of 33 documents
Electrical and optical low frequency noises in multimodal vertical cavity surface emitting lasers
2006
Experimental investigations of the low frequency noise of multimode 780 nm vertical cavity surface emitting lasers are reported. Electrical noise, optical noise and their correlation have been measured in the frequency range 1 Hz–95 kHz. The results show that the main contribution to the electrical noise is located in the distributed Bragg reflector layers of the laser. The optical power and pump current noise sources are strongly correlated below and around the threshold, while are weakly correlated above threshold. It is argued that the noise in the optical power is due to both free injection carrier noise and optical gain fluctuations.
Characterization of different regimes in nonlinear liquid crystal models
2012
[EN] The range of validity of two models for nonlocal nonlinear optics in Nematic Liquid Crystals (NLC) is studied. Particularly the influence of the optical power and the initial position of the beam over its trajectory is studied when launching the beam with an offset in a planar cell. The main difference between both models is the dependence of the orientational angle with the optical field, either linear or nonlinear. The results demonstrate the critical role of the nonlinearity in the propagation of nematicons in NLC planar cells. © 2012 World Scientific Publishing Company.
Transient photoresponse and incident power dependence of high-efficiency germanium quantum dot photodetectors
2012
We report a systematic study of time-resolved and power-dependent photoresponse in high-efficiency germanium quantum dot photodetectors (Ge-QD PDs), with internal quantum efficiencies greater than 100 over a broad wavelength, reverse bias, and incident power range. Turn-on and turn-off response times (τ on and τ off) are shown to depend on series resistance, bias, optical power, and thickness (W QD) of the Ge-QD layer, with measured τ off values down to ∼40 ns. Two different photoconduction regimes are observed at low and high reverse bias, with a transition around -3 V. A transient current overshoot phenomenon is also observed, which depends on bias and illumination power. © 2012 American …
Wide Temperature Operation of 40-Gb/s 1550-nm Electroabsorption Modulated Lasers
2006
Electroabsorption modulated lasers (EMLs) exploiting the quantum confined Stark effect need thermoelectric coolers to achieve stable output power levels and dynamic extinction ratios. Temperature-independent operation is reported between 20/spl deg/C and 70/spl deg/C for InGaAlAs-InP-based monolithically integrated 1550-nm EMLs exploiting a shared active area at 40 Gb/s by actively controlling the electroabsorption modulator bias voltage. Dynamic extinction ratios of at least 8 dB and fiber-coupled mean modulated optical power of at least 0.85 mW are obtained over the mentioned temperature range.
Measuring the refractive state of an eye based on the intensity of the retinal reflex
2017
AbstractWhen examining the fundus of the eye with an ophthalmoscope, the intensity of the retinal reflex depends on the refractive state of the eye. In this study, application of this phenomenon for measuring the refractive state of the eye is demonstrated. First, a calibration curve relating the intensity of the retinal reflex and the refractive state was obtained using a model eye. Next, the intensity of the retinal reflex was measured while subjects were viewing a checker-board pattern, the distance of which was varied within the range from 0.17 to 1 m. Further, the relation between the refractive state and the optical power of the stimulus could be determined based on the measured light…
Large Depth-of-Field Integral Microscopy by Use of a Liquid Lens
2018
Integral microscopy is a 3D imaging technique that permits the recording of spatial and angular information of microscopic samples. From this information it is possible to calculate a collection of orthographic views with full parallax and to refocus computationally, at will, through the 3D specimen. An important drawback of integral microscopy, especially when dealing with thick samples, is the limited depth of field (DOF) of the perspective views. This imposes a significant limitation on the depth range of computationally refocused images. To overcome this problem, we propose here a new method that is based on the insertion, at the pupil plane of the microscope objective, of an electrical…
Scaling guidelines of a soliton-based power limiter for 2R-optical regeneration applications
2010
International audience; In this work, we report scaling rules for the design of an all-fibered soliton-based power limiter for reamplification and reshaping (2R) regeneration process. In particular, we propose general guidelines to fix the optimum fiber length and initial power of the regenerator. We quantitatively point out the optical power limiting effect of the device enabling a significant reduction of the amplitude jitter of a degraded signal. Influence of the initial level of amplitude jitter is discussed and the results are compared with a self-phase modulation-based configuration working in the normal dispersion regime. Realistic numerical simulations in the context of 160 Gbit/s s…
Power Profiles and In Vitro Optical Quality of Scleral Contact Lenses: Effect of the Aperture and Power
2017
To assess the power profile and in vitro optical quality of scleral contact lenses with different powers as a function of the optical aperture. The mini and semiscleral contact lenses (Procornea) were measured for five powers per design. The NIMO TR-1504 (Lambda-X) was used to assess the power profile and Zernike coefficients of each contact lens. Ten measurements per lens were taken at 3- and 6-mm apertures. Furthermore, the optical quality of each lens was described in Zernike coefficients, modulation transfer function, and point spread function (PSF). A convolution of each lens PSF with an eye-chart image was also computed. The optical power fluctuated less than 0.5 diopters (D) along th…
Responsivity measurements of N-on-P and P-on-N silicon photomultipliers in the continuous wave regime
2013
We report the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon P-type and N-type substrate respectively. Responsivity measurements have been performed with an incident optical power from tenths of picowatts to hundreds of nanowatts and on a broad spectrum, ranging from ultraviolet to near infrared (340-820 nm). For both classes of investigated SiPMs, responsivity shows flat response versus the optical incident power, when a preset overvoltage and wavelength is applied . More in detail, this linear behavior extends up to about 10 nW for lower overvoltages, while a shrink is observ…
Two-Color Single-Photon Emission from In As Quantum Dots: Toward Logic Information Management Using Quantum Light
2014
In this work, we propose the use of the Hanbury-Brown and Twiss interferometric technique and a switchable two-color excitation method for evaluating the exciton and noncorrelated electron-hole dynamics associated with single photon emission from indium arsenide (InAs) self-assembled quantum dots (QDs). Using a microstate master equation model we demonstrate that our single QDs are described by nonlinear exciton dynamics. The simultaneous detection of two-color, single photon emission from InAs QDs using these nonlinear dynamics was used to design a NOT AND logic transference function. This computational functionality combines the advantages of working with light/photons input/output device…