Copyright (c) 2011 All rights reserved. http://works.bepress.com/ddericks Recent documents in Dennis Derickson en-us Mon, 08 Aug 2011 11:01:46 PDT 3600 http://works.bepress.com/ddericks/34 http://works.bepress.com/ddericks/34 Tue, 05 Apr 2011 11:41:46 PDT The RF output power of Ge/Si n-i-p waveguide photodetectors is improved by increasing the load impedance. The maximum extracted RF power at 3GHz is 17.13dBm with a compression current of 42mA using a 100Ὠ load.

]]> Andrew L. Huard et al. Conference Proceedings http://works.bepress.com/ddericks/33 http://works.bepress.com/ddericks/33 Mon, 17 May 2010 15:11:20 PDT Brandon George and Dennis Derickson California Polytechnic State Univ. (USA) Wavelength tunable sampled grating distributed Bragg reflector (SG-DBR) lasers used for telecommunications applications have previously demonstrated the ability for linear frequency ramps covering the entire tuning range of the laser at 100 kHz repetition rates1. An individual SG-DBR laser has a typical tuning range of 50 nm. The InGaAs/InP material system often used with SG-DBR lasers allows for design variations that cover the 1250 to 1650 nm wavelength range. This paper addresses the possibility of concatenating the outputs of tunable SGDBR lasers covering adjacent wavelength ranges for enhancing the resolution of OCT measurements. This laser concatenation method is demonstrated by combining the 1525 nm to 1575 nm wavelength range of a "C Band" SG-DBR laser with the 1570nm to 1620 nm wavelength coverage of an "L-Band" SG-DBR laser. Measurements show that SGDBR lasers can be concatenated with a transition switching time of less than 50 ns with undesired leakage signals attenuated by 50 dB.

]]> Brandon George et al. Conference Proceedings http://works.bepress.com/ddericks/32 http://works.bepress.com/ddericks/32 Wed, 06 May 2009 11:14:03 PDT Electrooptic modulators built from GaAs/Al_xGa_1-xAs Fabry-Perot cavities operating up to 6.5 GHz are reported. The measured frequency response agrees well with the one predicted using an equivalent circuit model derived from high-speed electrical measurements. The parasitic capacitances have been reduced to approximately 30 fF by fabricating the devices on semi-insulating GaAs substrates and integrating them with on-wafer bound pads which have dimensions compatible with microwave coplanar probes.

]]> R. J. Simes et al. Articles http://works.bepress.com/ddericks/31 http://works.bepress.com/ddericks/31 Wed, 06 May 2009 11:14:02 PDT Dennis J. Derickson et al. Articles http://works.bepress.com/ddericks/30 http://works.bepress.com/ddericks/30 Wed, 06 May 2009 11:14:01 PDT Dennis J. Derickson et al. Articles http://works.bepress.com/ddericks/28 http://works.bepress.com/ddericks/28 Wed, 06 May 2009 11:14:00 PDT A new mode-locking technique, self-mode-locking, is described which uses the detected optical pulses from the mode-locked laser as the active driving source. This technique forms narrow-width mode-locked optical pulses at low repetition rates without the use of a microwave synthesizer

]]> Dennis J. Derickson et al. Articles http://works.bepress.com/ddericks/27 http://works.bepress.com/ddericks/27 Wed, 06 May 2009 11:13:59 PDT A comprehensive timing jitter comparison is made for mode-locked semiconductor lasers using active, passive, and hybrid mode-locking techniques in both external and monolithic cavity configurations. Active mode locking gives the lowest residual rms timing jitter of 65 fs (150 Hz-50 MHz), followed by the hybrid and passive mode-locking techniques. It is found that monolithic cavity devices with all active waveguides have higher timing jitter levels than the comparable external cavity case.

]]> Dennis J. Derickson et al. Articles http://works.bepress.com/ddericks/26 http://works.bepress.com/ddericks/26 Wed, 06 May 2009 11:13:58 PDT Imperfect antireflection coatings in external-cavity mode-locked semiconductor lasers can cause multiple output pulse generation. The incorporation of an intrawaveguide saturable absorber segment into the laser suppresses this problem. Single pulse outputs of less than 2.8 ps and 0.7 pJ of energy are obtained using such devices with both quantum well and bulk active regions

]]> Dennis J. Derickson et al. Articles http://works.bepress.com/ddericks/25 http://works.bepress.com/ddericks/25 Wed, 06 May 2009 11:13:57 PDT Mode-locked vertical cavity lasers have a large cross-sectional area and consequently a large saturation energy and large peak powers. The authors analyze excess optical bandwidth generation in these lasers and find that self-phase modulation due to optical pumping and gain saturation is the dominant factor in inducing laser pulse chirping. The large magnitude of the chirp makes intracavity prism-pair compensation difficult. Adjustment of the cavity length has a major impact on the pulse chirping, as observed experimentally. Proper adjustment can result in a large linear frequency chirp which can be compensated using external pulse compression techniques

]]> Wenbin Jiang et al. Articles http://works.bepress.com/ddericks/24 http://works.bepress.com/ddericks/24 Wed, 06 May 2009 11:13:56 PDT The repetition frequency of an external cavity mode-locked GaAs semiconductor diode laser has been stabilized by voltage controlled electrical feedback. The phase noise has been reduced by 40dB at 1 kHz offset from the carrier and timing jitter reduced from more than 30ps to 4ps. This technique can be used to stabilize millimetre-wave mode-locked lasers.

]]> R. J. Helkey et al. Articles http://works.bepress.com/ddericks/23 http://works.bepress.com/ddericks/23 Wed, 06 May 2009 11:13:56 PDT A report is presented on the design, fabrication, testing, and modeling of single-heterojunction Al_0.27Ga_0.73As/Ga p-i-n photodiodes for use as components in optical receivers. The photodiodes are grown by molecular beam epitaxy and fabricated as 1100-μm² mesa structures. At 5-V reverse bias and 850 nm, 100 fF of capacitance, 90 pA of leakage current, 73% external quantum efficiency, <2% reflectivity, and 22-GHz bandwidths are typically measured.

]]> C. Johnson et al. Articles http://works.bepress.com/ddericks/22 http://works.bepress.com/ddericks/22 Wed, 06 May 2009 11:13:55 PDT Absorption recovery dynamics of GaAs/AlGaAs field-enhanced waveguide saturable absorbers are studied by pump-probe differential transmission measurements. We compare the response of bulk and single quantum well absorbers at different reverse bias levels and pump powers, and find an ultrafast transient in the response, followed by a slower rise before the final recovery. The absorption fully recovers after a few picoseconds, which is an important result for mode-locked lasers.

]]> J. R. Karin et al. Articles http://works.bepress.com/ddericks/29 http://works.bepress.com/ddericks/29 Wed, 06 May 2009 11:13:55 PDT Microwave and millimeter wave signals can be generated using mode-locked semiconductor lasers with intra-waveguide saturable absorbers. Monolithic and external cavity devices optimized for electrical and optical signal generation are discussed along with measurements of amplitude noise, phase noise, output power, and repetition rate tunability.

]]> Dennis J. Derickson et al. Conference Proceedings http://works.bepress.com/ddericks/21 http://works.bepress.com/ddericks/21 Wed, 06 May 2009 11:13:31 PDT A photoreceiver consisting of a high-speed p-i-n photodetector and a 100-kHz to 22-GHz distributed amplifier is described. Photoreceiver calibration is accomplished by optical heterodyne techniques. The photoreceiver is used with a microwave spectrum analyzer to produce a fully amplitude-calibrated 22-GHz-bandwidth lightwave signal analyzer system for displaying intensity-modulated light with -65-dB (optical) sensitivity at 1300-nm and 1550-nm wavelengths.

]]> Dennis J. Derickson et al. Conference Proceedings http://works.bepress.com/ddericks/19 http://works.bepress.com/ddericks/19 Mon, 04 May 2009 09:48:36 PDT This paper describes novel semiconductor sources for optical low coherence reflectometry (OLCR), a measurement technique for characterizing device and fiber reflections with high sensitivity and high spatial resolution. Lasers and conventional superluminescent LEDs are not suitable for OLCR because strong reflections from the back facets mask weak reflection signals from the device or fiber under test. Even standard edge emitting LEDs (EELEDs) show significant reflections, which have limited the dynamic range of previous measurements. Low source output powers have also limited sensitivity. In order to obtain high power while minimizing internal reflections, a high single pass gain device is required. The record combination of high power and low internal reflections of the InGaAsP EELEDs reported here significantly expands the dynamic range and sensitivity of LED based reflectometry at 1.5 μm. This work also compares the characteristics of quantum well and bulk EELEDs.

]]> J. E. Fouquet et al. Conference Proceedings http://works.bepress.com/ddericks/20 http://works.bepress.com/ddericks/20 Mon, 04 May 2009 09:48:36 PDT Roger Helkey et al. Conference Proceedings http://works.bepress.com/ddericks/18 http://works.bepress.com/ddericks/18 Mon, 04 May 2009 09:48:35 PDT J. G. Wasserbauer et al. Conference Proceedings http://works.bepress.com/ddericks/17 http://works.bepress.com/ddericks/17 Mon, 04 May 2009 09:48:21 PDT We report the first mode-locked operation of a resonant optical waveguide (ROW semiconductor laser array. Pulsewidths as short as 23 ps and peak powers of over 1W are generated in a single-lobed beam.

]]> Alan Mar et al. Conference Proceedings http://works.bepress.com/ddericks/15 http://works.bepress.com/ddericks/15 Fri, 01 May 2009 15:51:53 PDT Microwave signal generation using self-heterodyning of a single wavelength tunable SG-DBR laser is demonstrated. Microwave signals are established by quickly hopping back and forth between two optical wavelengths. These wavelengths are made time coincident through a delay line interferometer. The output of the interferometer is photodetected resulting in a CW microwave signal. This method does not require conventional master-slave laser configurations, external microwave drive sources, or a mode locked laser used to beat dual longitudinal modes. Microwave signals up to 12 GHz have been measured by frequency modulating the phase section of the SG-DBR laser with low frequency RF square wave input currents. Millimeter wave difference frequencies are easily available from the SG-DBR. Temperature robustness of SG-DBR self-heterodyne signals was also investigated. While each laser wavelength by itself changes by 0.12 nm/C (21 GHz/C), the difference frequency temperature coefficient is well less than 30 MHz/C typically.

]]> Michael A. Bernacil et al. Conference Proceedings http://works.bepress.com/ddericks/16 http://works.bepress.com/ddericks/16 Fri, 01 May 2009 15:51:53 PDT A detector array spectrometer simultaneously monitors wavelength, power, and signal-to-noise ratio of wavelength division multiplexed (WDM) channels in telecommunication networks. A spectrometer spatially separates signals from the WDM channels according to the channels' wavelengths. The separated signals are incident on an array of split-detectors that conforms to the spatial separation of the signals provided by the spectrometer. While the split-detectors are positioned to receive a signal from each WDM channel, a noise detector is positioned between adjacent split-detectors to measure noise. A common mode output from two halves of each split-detector indicates the power in a WDM channel, while a differential output from the halves indicates wavelength deviations in the WDM channels. The ratio of the common mode signal to the noise detector signal is used to monitor the signal-to-noise ratio of the WDM channel. An angled diffraction grating in the spectrometer achieves compact size and high measurement resolution for the detector array spectrometer.

]]> Dennis J. Derickson et al. Patents