Broadband polarization-insensitive semiconductor optical amplifier gate with tensile InGaAs quasi-bulk and compressively strained InGaAs wells

A novel wideband polarization-insensitive semiconductor optical amplifier (SOA) gate containing compressively strained InGaAs quantum wells and tensile-strained InGaAs quasi-bulk layers is developed. The fabricated SOA gates have a wide 3-dB optical bandwidth of 102 nm, less than 0.8-dB polarization sensitivity, more than 50-dB extinction ratio, and less than 75-mA fiber-to-fiber lossless operating current. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

A novel extremely broadband superluminescent diode based on symmetric graded tensile-strained bulk InGaAs

A novel broadband superluminescent diode (SLD), which has a symmetric graded tensile-strained bulk InGaAs active region, is developed. The symmetric-graded tensile-strained bulk InGaAs is achieved by changing the group III TMGa source flow only during its growth process by low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE), in which the much different tensile strain is introduced simultaneously. At 200mA injection current, the full width at half maximum (FWHM) of the emission spectrum of the SLID can be up to 122nm, covering the range of 1508-1630nm, and the output power is 11.5mW.

A novel design of grating couplers for efficient broadband coupling between silicon-on-insulator nanophotonic waveguides and fibres

A novel design of out-of-plane grating couplers is proposed for coupling between silicon-on-insulator nanophotonic waveguides and single-mode fibres. The coupler with the first-order diffraction coupling to the optical fibre is actually a second-order reflected grating with two times of period of the first-order grating. To enhance outcoupled power, a back hole is designed to form in the silicon substrate and a kind of metals is placed on the top acting as a reflection layer. The coupler is optimized using coupled-mode- based simulations, showing that, the coupling efficiency to and from tapered optical fibre can be as high as 85% with 1 dB bandwidth about 23nm.

A broadband external cavity tunable InAs/GaAs quantum dot laser by utilizing only the ground state emission

A broadband external cavity tunable laser is realized by using a broad-emitting spectral InAs/GaAs quantum dot (QD) gain device. A tuning range of 69 nm with a central wavelength of 1056 nm, is achieved at a bias of 1.25 kA/cm(2) only by utilizing the light emission from the ground state of QDs. This large tunable range only covers the QD ground-state emission and is related to the inhomogeneous size distribution of QDs. No excited state contributes to the tuning bandwidth. The application of the QD gain device to the external cavity tunable laser shows its immense potential in broadening the tuning bandwidth. By the external cavity feedback, the threshold current density can be reduced remarkably compared with the free-running QD gain device.

Broadband external cavity tunable quantum dot lasers with low injection current density

Broadband grating-coupled external cavity laser, based on InAs/GaAs quantum dots, is achieved. The device has a wavelength tuning range from 1141.6 nm to 1251.7 nm under a low continuous-wave injection current density (458 A/cm(2)). The tunable bandwidth covers consecutively the light emissions from both the ground state and the 1st excited state of quantum dots. The effects of cavity length and antireflection facet coating on device performance are studied. It is shown that antireflection facet coating expands the tuning bandwidth up to similar to 150 nm, accompanied by an evident increase in threshold current density, which is attributed to the reduced interaction between the light field and the quantum dots in the active region of the device.

Ultra-broadband optical parametric chirped-pulse amplification by matching of both group-velocity and pulse-front

Ultra-broadband optical parametric chirped-pulse amplification is analyzed based the compensation of phase-mismatch, which is achieved by matching of both group-velocity and pulse-front between signal and idler by the combination of the noncollinear-phase-match and pulse-front-tilt. The results show exactly matching of both group-velocity and pulse-front is the important criterion for constructing an UBOPCPA. Its general model is developed, in which the group velocities, noncollinear angles. spatial walk-off angles, linear angular spectral dispersion coefficients and pulse-front tilted angles are suitably linked to each other. Finally, specific numerical calculations and simulations are presented for beta-barium borate OPCPA with type-1 noncollinear angularly dispersed geometry. (C) 2005 Elsevier B.V. All rights reserved.

Pulse-front matched ultra-broadband optical parametric chirped pulse amplifier for sub-12 fs pulse generation

We propose a LBO-based ultra-broadband chirped pulse optical parametric amplifier employing pulse-front-matching to yield transform-limited sub-12-fs pulses. Measurement of the maximum possible gain bandwidth for the LBO-based OPCPA demonstrates more than 60nm gain bandwidth FWHM. For the generation of TL pulses by the use of this OPCPA, a suitable combination of OPCPA and PFM is first presented. The PFM pump geometry realizes tilt-free signal amplification, and permits this OPCPA to generate TL sub-12-fs pulses.

Zero-broadening SBS slow light propagation in an optical fiber using two broadband pump beams

A new method of tailoring stimulated Brillouin scattering (SBS) gain spectrum for slow light propagation is proposed by use of two Gaussian-shaped broadband pump beams with different powers and spectral widths. The central frequency interval between the two pump beams are carefully set to be two inherent Brillouin frequency shift, ensuring that the gain spectrum of one pump has the same central frequency with the loss spectrum of the other one. Different gain profiles are obtained and analyzed. Among them a special gain profile is found that ensures a zero-broadening of the signal pulse independent of the Brillouin gain. This is owing to the compensation between the positive gain-dependent broadening and the negative GVD (group velocity dispersion) dependent broadening. The relationship of two pump beams is also found for constructing such a gain profile. It provides us a new idea of managing the broadening of SBS-based slow pulse by artificially constructing and optimizing the profile of gain spectrum. (c) 2008 Optical Society of America.

Broadband terahertz time-domain spectroscopy of drugs-of-abuse and the use of principal component analysis

EPSRC, the European Community IST FP6 Integrated, etc

Distortion management of SBS slow light in a single-mode optical fiber by optimization of broadband SBS gain spectrum

SPIE