Fast tuneable InGaAsP DBR laser using quantum-confined stark-effect-induced refractive index change

We report a monolithically integrated InGaAsP DBR ridge waveguide laser that uses the quantum-confined Stark effect (QCSE) to achieve fast tuning response. The laser incorporates three sections: a forward-biased gain section, a reverse-biased phase section, and a reverse-biased DBR tuning section. The laser behavior is modeled using transmission matrix equations and tuning over similar to 8 nm is predicted. Devices were fabricated using post-growth shallow ion implantation to reduce the loss in the phase and DBR sections by quantum well intermixing. The lasing wavelength was measured while varying the reverse bias of the phase and DBR sections in the range 0 V to < - 2.5 V. Timing was noncontinuous over a similar to 7-nm-wavelength range, with a side-mode suppression ratio of similar to 20 dB. Coupled cavity effects due to the fabrication method used introduced discontinuities in tuning. The frequency modulation (FM) response was measured to be uniform within 2 dB over the frequency range 10 MHz to 10 GHz, indicating that tuning times of 100 ps are possible

Nanosecond channel-switching exact optical frequency synthesizer using an optical injection phase-locked loop (OIPLL)

Experimental results are reported on an optical frequency synthesizer for use in dynamic dense wavelength-division-multiplexing networks, based on a tuneable laser in an optical injection phase-locked loop for rapid wavelength locking. The source combines high stability (50 dB), narrow linewidth (10 MHz), and fast wavelength switching (<10 ns)

100 GHz Spaced 10 Gbit/s WDM over 10 degrees C to 70 degrees C using an uncooled DBR laser

100 GHz spaced 10 Gbit/s (NRZ, PRBS 2(31)-1) WDM transmission is demonstrated with an uncooled DBR laser. The wavelength of the laser was stabilised within 2 GHz from 10 degrees C to 70 degrees C using a predicting algorithm. (C) 2004 Optical Society of America

A monolithic MQW InP/InGaAsP-based comb generator

We report a monolithic optical frequency comb generator using quaternary/quaternary multiple quantum well InV/InGaAsP material as phase modulator and gain medium in a Frequency Modulated (FM) laser design. The modulation was generated by quantum confined Stark effect to achieve a comb-line spacing of 24.4 GHz. The laser was fabricated using a single epitaxial growth step and quantum well intermixing to realize low loss phase and modulation sections. The resulting comb generator produces lines with a spacing exactly given by the modulation frequency, differential phase noise between adjacent lines of -82 dBc/Hz at 1 kHz offset and a comb spectrum width of up to 2 THz

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations

Electro-optical frequency division and stable microwave synthesis

A new method of optical frequency division is demonstrated using a tunable electrical oscillator to create combs through phase modulation of a dual Brillouin laser frequency reference. The method is used to generate stable microwaves

A monolithic MQW InP-InGaAsP-Based optical comb generator

We report the first demonstration of a monolithic optical-frequency comb generator. The device is based on multi-section quaternary/quaternary eight-quantum-well InP-InGaAsP material in a frequency-modulated (FM) laser design. The modulation is generated using quantum-confined Stark-effect phase-induced refractive index modulation to achieve fast modulation up to 24.4 GHz. The laser was fabricated using a single epitaxial growth step and quantum-well intermixing to realize low-loss phase adjustment and modulation sections. The output was quasicontinuous wave with intensity modulation at less than 20% for a total output power of 2 mW. The linewidth of each line was limited by the linewidth of the free running laser at an optimum of 25 MHz full-width at half-maximum. The comb generator produces a number of lines with a spacing exactly equal to the modulation frequency (or a multiple of it), differential phase noise between adjacent lines of -82 dBc/Hz at 1-kHz offset (modulation source-limited), and a potential comb spectrum width of up to 2 THz (15 nm), though the comb spectrum was not continuous across the full span

Integrated Semiconductor Laser Optical Phase Lock Loops

An Optical Phase Lock Loop (OPLL) is a feedback control system that allows the phase stabilization of a laser to a reference laser with absolute but adjustable frequency offset. Such phase and frequency locked optical oscillators are of great interest for sensing, spectroscopy, and optical communication applications, where coherent detection offers advantages of higher sensitivity and spectral efficiency than can be achieved with direct detection. As explained in this paper, the fundamental difficulty in realising an OPLL is related to the limitations on loop bandwidth and propagation delay as a function of laser linewidth. In particular, the relatively wide linewidth of semiconductor lasers requires short delay, which can only be achieved through shortening of the feedback path, which is greatly facilitated through photonic integration. This paper reviews the advances in the development of semiconductor laser-based OPLLs and describes how improvements in performance have been enabled by improvements in photonic integration technology. We also describe the first OPLL created using foundry fabricated photonic integrated circuits and off-the-shelf electronic components. Stable locking has been achieved for offset frequencies between 4 and 12 GHz with a heterodyne phase noise below -100 dBc/Hz at 10 kHz offset. This is the highest performance yet reported for a monolithically integrated OPLL and demonstrates the attractiveness of the foundry fabrication approach

III-V Quantum Dot Lasers Epitaxially Grown on Si

Monolithic integration of semiconductor lasers on silicon platform is the ultimate solution for creating complex optoelectronic circuits, which is the key to chip-to-chip and system-to-system communications. The direct epitaxial integration of III-V semiconductor materials on Si or Ge is one of the most promising approaches for the fabrication of electrically pumped light sources on a Si platform, promising low-cost, high-yield and large-scale deployment of silicon photonics [1], [2]. However, monolithic integration technique faces significant challenges because of the large material dissimilarity between III-V and Group IV materials, such as lattice mismatch, thermal expansion coefficient differences, and polar versus nonpolar surfaces [2], [3]. These differences tend to produce various types of defects, such as, antiphase boundaries (APBs), threading dislocations (TDs), and microcracks, which all generate nonradiative recombination centers and dramatically undermine the promise of III-V materials. Recently, quantum dots (QDs) structure is becoming widely used in active layer in semiconductor lasers due to their advantages of low threshold current density and temperature insensitive operation [4], [5]. Also, QD structures have attracted increasing attention for the monolithic III-V/Si integration due to their enhanced tolerance to defects and special capability of filtering the APBs and threading dislocations [6], [7]. In this paper, we review our recent progress made in the direct growth of III-V QD lasers on Si substrates