The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Oskar Painter - One of the best experts on this subject based on the ideXlab platform.

  • Optical Loss and lasing characteristics of high quality factor algaas microdisk resonators with embedded quantum dots
    Applied Physics Letters, 2005
    Co-Authors: Kartik Srinivasan, Matthew Borselli, Thomas J Johnson, Oskar Painter, Paul E Barclay, A Stintz, Sanjay Krishna
    Abstract:

    Optical characterization of AlGaAs microdisk resonant cavities with a quantum dot active region is presented. Direct passive measurement of the Optical Loss within AlGaAs microdisk resonant structures embedded with InAs/InGaAs dots-in-a-well (DWELL) is performed using an Optical-fiber-based probing technique at a wavelength (λ ~ 1.4 μm) that is red detuned from the dot emission wavelength (λ ~ 1.2 μm). Measurements in the 1.4 μm wavelength band on microdisks of diameter D=4.5 μm show that these structures support modes with cold-cavity quality factors as high as 3.6 x 10^(5). DWELL-containing microdisks are then studied through Optical pumping at room temperature. Pulsed lasing at λ ~ 1.2 μm is seen for cavities containing a single layer of InAs dots, with threshold values of ~ 17 μW, approaching the estimated material transparency level. Room-temperature continuous-wave operation is also observed.

  • beyond the rayleigh scattering limit in high q silicon microdisks theory and experiment
    Optics Express, 2005
    Co-Authors: Matthew Borselli, Thomas J Johnson, Oskar Painter
    Abstract:

    Using a combination of resist reflow to form a highly circular etch mask pattern and a low-damage plasma dry etch, high-quality-factor silicon Optical microdisk resonators are fabricated out of silicon-on-insulator (SOI) wafers. Quality factors as high as Q = 5×10^6 are measured in these microresonators, corresponding to a propagation Loss coefficient as small as α ~ 0.1 dB/cm. The different Optical Loss mechanisms are identified through a study of the total Optical Loss, mode coupling, and thermally-induced Optical bistability as a function of microdisk radius (5-30 µm). These measurements indicate that Optical Loss in these high-Q microresonators is limited not by surface roughness, but rather by surface state absorption and bulk free-carrier absorption.

  • rayleigh scattering mode coupling and Optical Loss in silicon microdisks
    Applied Physics Letters, 2004
    Co-Authors: Matthew Borselli, Kartik Srinivasan, Paul E Barclay, Oskar Painter
    Abstract:

    High refractive index contrast Optical microdisk resonators fabricated from silicon-on-insulator wafers are studied using an external silica fiber taper waveguide as a wafer-scale Optical probe. Measurements performed in the 1500 nm wavelength band show that these silicon microdisks can support whispering-gallery modes with quality factors as high as 5.2×10^5, limited by Rayleigh scattering from fabrication induced surface roughness. Microdisks with radii as small as 2.5 µm are studied, with measured quality factors as high as 4.7×10^5 for an Optical mode volume of 5.3 (lambda/n)^3.

Matthew Borselli - One of the best experts on this subject based on the ideXlab platform.

  • Optical Loss and lasing characteristics of high quality factor algaas microdisk resonators with embedded quantum dots
    Applied Physics Letters, 2005
    Co-Authors: Kartik Srinivasan, Matthew Borselli, Thomas J Johnson, Oskar Painter, Paul E Barclay, A Stintz, Sanjay Krishna
    Abstract:

    Optical characterization of AlGaAs microdisk resonant cavities with a quantum dot active region is presented. Direct passive measurement of the Optical Loss within AlGaAs microdisk resonant structures embedded with InAs/InGaAs dots-in-a-well (DWELL) is performed using an Optical-fiber-based probing technique at a wavelength (λ ~ 1.4 μm) that is red detuned from the dot emission wavelength (λ ~ 1.2 μm). Measurements in the 1.4 μm wavelength band on microdisks of diameter D=4.5 μm show that these structures support modes with cold-cavity quality factors as high as 3.6 x 10^(5). DWELL-containing microdisks are then studied through Optical pumping at room temperature. Pulsed lasing at λ ~ 1.2 μm is seen for cavities containing a single layer of InAs dots, with threshold values of ~ 17 μW, approaching the estimated material transparency level. Room-temperature continuous-wave operation is also observed.

  • beyond the rayleigh scattering limit in high q silicon microdisks theory and experiment
    Optics Express, 2005
    Co-Authors: Matthew Borselli, Thomas J Johnson, Oskar Painter
    Abstract:

    Using a combination of resist reflow to form a highly circular etch mask pattern and a low-damage plasma dry etch, high-quality-factor silicon Optical microdisk resonators are fabricated out of silicon-on-insulator (SOI) wafers. Quality factors as high as Q = 5×10^6 are measured in these microresonators, corresponding to a propagation Loss coefficient as small as α ~ 0.1 dB/cm. The different Optical Loss mechanisms are identified through a study of the total Optical Loss, mode coupling, and thermally-induced Optical bistability as a function of microdisk radius (5-30 µm). These measurements indicate that Optical Loss in these high-Q microresonators is limited not by surface roughness, but rather by surface state absorption and bulk free-carrier absorption.

  • rayleigh scattering mode coupling and Optical Loss in silicon microdisks
    Applied Physics Letters, 2004
    Co-Authors: Matthew Borselli, Kartik Srinivasan, Paul E Barclay, Oskar Painter
    Abstract:

    High refractive index contrast Optical microdisk resonators fabricated from silicon-on-insulator wafers are studied using an external silica fiber taper waveguide as a wafer-scale Optical probe. Measurements performed in the 1500 nm wavelength band show that these silicon microdisks can support whispering-gallery modes with quality factors as high as 5.2×10^5, limited by Rayleigh scattering from fabrication induced surface roughness. Microdisks with radii as small as 2.5 µm are studied, with measured quality factors as high as 4.7×10^5 for an Optical mode volume of 5.3 (lambda/n)^3.

Nasser N Peyghambarian - One of the best experts on this subject based on the ideXlab platform.

  • sol gel material enabled electro optic polymer modulators
    Sensors, 2015
    Co-Authors: Roland Himmelhuber, Yasufumi Enami, Robert A Norwood, Nasser N Peyghambarian
    Abstract:

    Sol-gels are an important material class, as they provide easy modification of material properties, good processability and are easy to synthesize. In general, an electro-optic (EO) modulator transforms an electrical signal into an Optical signal. The incoming electrical signal is most commonly information encoded in a voltage change. This voltage change is then transformed into either a phase change or an intensity change in the light signal. The less voltage needed to drive the modulator and the lower the Optical Loss, the higher the link gain and, therefore, the better the performance of the modulator. In this review, we will show how sol-gels can be used to enhance the performance of electro-optic modulators by allowing for designs with low Optical Loss, increased poling efficiency and manipulation of the electric field used for driving the modulator. The Optical Loss is influenced by the propagation Loss in the device, as well as the Losses occurring during fiber coupling in and out of the device. In both cases, the use of sol-gel materials can be beneficial due to the wide range of available refractive indices and low Optical attenuation. The influence of material properties and synthesis conditions on the device performance will be discussed.

  • transversely tapered hybrid electro optic polymer sol gel mach zehnder waveguide modulators
    Applied Physics Letters, 2008
    Co-Authors: Yasufumi Enami, D Mathine, Christopher T Derose, Robert A Norwood, Nasser N Peyghambarian
    Abstract:

    We show results of a proposed hybrid modulator structure that reduces both the Optical Loss and half wave voltage (Vπ). A sol-gel waveguide core transversely sandwiched between two Mach–Zehnder arms of electro-optic (EO) polymer cores enables an adiabatic transverse transition between the sol-gel and the EO polymer cores without the need for Y branches. The undercladding thickness is reduced to 3.7μm with negligible further Optical Loss from the bottom electrode. EO modulation with Vπ of 1.8V at 1550nm is demonstrated using a guest-host EO polymer, with an Optical insertion Loss of 13.7dB in the transverse magnetic mode.

Kartik Srinivasan - One of the best experts on this subject based on the ideXlab platform.

  • Optical Loss and lasing characteristics of high quality factor algaas microdisk resonators with embedded quantum dots
    Applied Physics Letters, 2005
    Co-Authors: Kartik Srinivasan, Matthew Borselli, Thomas J Johnson, Oskar Painter, Paul E Barclay, A Stintz, Sanjay Krishna
    Abstract:

    Optical characterization of AlGaAs microdisk resonant cavities with a quantum dot active region is presented. Direct passive measurement of the Optical Loss within AlGaAs microdisk resonant structures embedded with InAs/InGaAs dots-in-a-well (DWELL) is performed using an Optical-fiber-based probing technique at a wavelength (λ ~ 1.4 μm) that is red detuned from the dot emission wavelength (λ ~ 1.2 μm). Measurements in the 1.4 μm wavelength band on microdisks of diameter D=4.5 μm show that these structures support modes with cold-cavity quality factors as high as 3.6 x 10^(5). DWELL-containing microdisks are then studied through Optical pumping at room temperature. Pulsed lasing at λ ~ 1.2 μm is seen for cavities containing a single layer of InAs dots, with threshold values of ~ 17 μW, approaching the estimated material transparency level. Room-temperature continuous-wave operation is also observed.

  • rayleigh scattering mode coupling and Optical Loss in silicon microdisks
    Applied Physics Letters, 2004
    Co-Authors: Matthew Borselli, Kartik Srinivasan, Paul E Barclay, Oskar Painter
    Abstract:

    High refractive index contrast Optical microdisk resonators fabricated from silicon-on-insulator wafers are studied using an external silica fiber taper waveguide as a wafer-scale Optical probe. Measurements performed in the 1500 nm wavelength band show that these silicon microdisks can support whispering-gallery modes with quality factors as high as 5.2×10^5, limited by Rayleigh scattering from fabrication induced surface roughness. Microdisks with radii as small as 2.5 µm are studied, with measured quality factors as high as 4.7×10^5 for an Optical mode volume of 5.3 (lambda/n)^3.

Nikita A. Pikhtin - One of the best experts on this subject based on the ideXlab platform.

  • Study of the Spatial and Current Dynamics of Optical Loss in Semiconductor Laser Heterostructures by Optical Probing
    Semiconductors, 2020
    Co-Authors: P. S. Gavrina, Sergey O. Slipchenko, O. S. Soboleva, A. A. Podoskin, A. E. Kazakova, V. A. Kapitonov, Nikita A. Pikhtin
    Abstract:

    The spatial and temporal dynamics of the Optical Loss and carrier density in the heterostructure of a semiconductor laser with a segmented contact are studied using an Optical pump–probe technique based on the injection of probe radiation with a wavelength of 1560 nm into a semiconductor laser chip under study that is based on an AlGaAs/InGaAs/GaAs heterostructure and emits at wavelength of 1010 nm. It is demonstrated that employing probe light at a wavelength of 1560 nm enables sensitivity in measuring an internal Optical Loss of no less than 1 cm–1. The segmented design of the current pumping region made it possible to estimate the absolute internal Optical Loss. It is shown that changing the configuration of the Fabry–Perot eigenmodes of the laser affects the carrier distribution and the internal Optical Loss both in the current pumping region and in the passive, current unpumped part of the laser chip.

  • Switching Control Model of Closed-Mode Structures in Large Rectangular Cavities Based on AlGaAs/InGaAs/GaAs Laser Heterostructures
    Semiconductors, 2020
    Co-Authors: A. A. Podoskin, Sergey O. Slipchenko, Z. N. Sokolova, P. S. Gavrina, I. S. Shashkin, D. N. Romanovich, Nikita A. Pikhtin
    Abstract:

    A lumped model of the dynamics of the controlled switching of high- Q closed-mode structures in rectangular large cavities (up to 1 × 1 mm and larger) based on AlGaAs/InGaAs/GaAs laser heterostructures is presented. The model considers the modulation of the useful power of a closed-mode structure due to controlled generation switching to an alternative closed mode. Generation-switching control between closed mode structures is implemented due to a variation in the Optical Loss of one structure. A variation in the Optical Loss occurs due to an increase in interband Optical absorption due to the quantum-confined Stark effect upon the application of voltage to a laser crystal segment in the closed-mode propagation region.

  • Measurements of internal Optical Loss inside an operating laser diode
    Journal of Applied Physics, 2019
    Co-Authors: D A Veselov, Sergey O. Slipchenko, Yu. K. Bobretsova, Andrey Yu. Leshko, V. V. Shamakhov, Nikita A. Pikhtin
    Abstract:

    An experimental technique for measuring internal Optical Loss in high-power edge-emitting semiconductor lasers is demonstrated. The technique is based on coupling a probe beam into the waveguide of a pulse-pumped laser diode. It allows measuring free-carrier absorption (FCA) in a laser heterostructure at different temperatures and at pump current levels up to 30 kA/cm2. Measurement results are presented for two laser heterostructure designs, which vary in the waveguide doping level and material. For both heterostructures, the pump current increase induces a significant rise in FCA and a corresponding increase in internal Optical Loss, from 0.4–0.7 cm−1 at the threshold current to 2–2.5 cm−1 at 15 kA/cm2. At higher temperatures, the dependence is even stronger and the internal Optical Loss rises to 6 cm−1 (65 °C, 27 kA/cm2). The gradient of the FCA current dependence is lower for the laser heterostructure with a doped GaAs waveguide, while the heterostructure with an undoped AlGaAs waveguide displays a larger increase in FCA but better internal quantum efficiency at high currents. These results show that the proposed experimental method has significant potential.An experimental technique for measuring internal Optical Loss in high-power edge-emitting semiconductor lasers is demonstrated. The technique is based on coupling a probe beam into the waveguide of a pulse-pumped laser diode. It allows measuring free-carrier absorption (FCA) in a laser heterostructure at different temperatures and at pump current levels up to 30 kA/cm2. Measurement results are presented for two laser heterostructure designs, which vary in the waveguide doping level and material. For both heterostructures, the pump current increase induces a significant rise in FCA and a corresponding increase in internal Optical Loss, from 0.4–0.7 cm−1 at the threshold current to 2–2.5 cm−1 at 15 kA/cm2. At higher temperatures, the dependence is even stronger and the internal Optical Loss rises to 6 cm−1 (65 °C, 27 kA/cm2). The gradient of the FCA current dependence is lower for the laser heterostructure with a doped GaAs waveguide, while the heterostructure with an undoped AlGaAs waveguide displays a lar...

  • increase in the internal Optical Loss with increasing pump current and the output power of quantum well lasers
    Semiconductors, 2017
    Co-Authors: Z. N. Sokolova, Nikita A. Pikhtin, I S Tarasov, D A Veselov, L V Asryan
    Abstract:

    The operating characteristics of semiconductor quantum-well lasers, calculated with consideration for an increase in the internal Optical Loss in the waveguide region with increasing pump current, are presented. The condition of global electroneutrality in the structure is used. This condition consists in that the total charge of electrons in the 2D active region (quantum well) and bulk waveguide region (Optical confinement layer) is equal to the total charge of holes in these two regions. Good agreement between the calculated and experimentally determined light–current characteristics is obtained.

  • On the problem of internal Optical Loss and current leakage in laser heterostructures based on AlGaInAs/InP solid solutions
    Semiconductors, 2016
    Co-Authors: D A Veselov, Nikita A. Pikhtin, Sergey O. Slipchenko, I. S. Shashkin, K. V. Bakhvalov, A. V. Lyutetskiy, M. G. Rastegaeva, E. A. Bechvay, V. A. Strelets, V. V. Shamakhov
    Abstract:

    Semiconductor lasers based on MOCVD-grown AlGaInAs/InP separate-confinement heterostructures are studied. It is shown that raising only the energy-gap width of AlGaInAs-waveguides without the introduction of additional barriers results in more pronounced current leakage into the cladding layers. It is found that the introduction of additional barrier layers at the waveguide–cladding-layer interface blocks current leakage into the cladding layers, but results in an increase in the internal Optical Loss with increasing pump current. It is experimentally demonstrated that the introduction of blocking layers makes it possible to obtain maximum values of the internal quantum efficiency of stimulated emission (92%) and continuouswave output Optical power (3.2 W) in semiconductor lasers in the eye-safe wavelength range (1400–1600 nm).