Semiconductor Laser Chip Research Articles

Chaos laser chips with delayed optical feedback using a passive ring waveguide

We report a novel chaos semiconductor laser chip in which a distributed feedback (DFB) laser, two semiconductor optical amplifiers (SOAs) and a photodiode (PD) are monolithically integrated with a passive ring waveguide. The ring-type structure with the two separate SOAs achieves stronger delayed optical feedback compared to previous chaos laser chips which use linear waveguide and facet-reflection. The integrated PD allows efficient detection of the optical signal with low optical loss. A rich variety of dynamical behaviors and optical signals can be selectively generated via injection currents to the two separate SOAs. In particular, the strong optical feedback makes possible the generation of strong broadband optical chaos, with very flat spectrum of ±6.5 dB up to 10 GHz. The stability and quality of the chaotic mode is demonstrated using strict statistical tests of randomness applied to long binary sequences extracted by sampling the optical intensity signal.

All-polymer organic semiconductor laser chips: Parallel fabrication and encapsulation

Organic semiconductor lasers are of particular interest as tunable visible laser light sources. For bringing those to market encapsulation is needed to ensure practicable lifetimes. Additionally, fabrication technologies suitable for mass production must be used. We introduce all-polymer chips comprising encapsulated distributed feedback organic semiconductor lasers. Several chips are fabricated in parallel by thermal nanoimprint of the feedback grating on 4″ wafer scale out of poly(methyl methacrylate) (PMMA) and cyclic olefin copolymer (COC). The lasers consisting of the organic semiconductor tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM) are hermetically sealed by thermally bonding a polymer lid. The organic thin film is placed in a basin within the substrate and is not in direct contact to the lid. Thus, the spectral properties of the lasers are unmodified in comparison to unencapsulated lasers. Grating periods of 378 nm to 428 nm in steps of 10 nm result in lasing at wavelengths of 622 nm to 685 nm. The operational lifetime of the lasers expressed in number of pulses is improved 11-fold (PMMA) and 3-fold (COC) in comparison to unencapsulated PMMA devices.

Discretely tunable micromachined injection-locked lasers

This paper reports a micromachined injection-locked laser (ILL) to provide tunable discrete wavelengths. It utilizes a non-continuously tunable laser as the master to lock a Fabry–Pérot semiconductor laser chip. Both lasers are integrated into a deep-etched silicon chip with dimensions of 3 mm × 3 mm × 0.8 mm. Based on the experimental results, significant improvements in the optical power and spectral purity have been achieved in the fully locked state, and optical hysteresis and bistability have also been observed in response to the changes of the output wavelength and optical power of the master laser. As a whole system, the micromachined ILL is able to provide single mode, discrete wavelength tuning, high power and direct modulation with small size and single-chip solution, making it promising for advanced optical communications such as wavelength division multiplexing optical access networks.

Characterization of parasitics from scattering parameters of laser diode

AbstractA novel method for characterizing the parasitics of parasitic network is proposed based on the relations between the scattering parameters of a semiconductor laser chip and laser diode. Experiments are designed and performed using our method. The analysis results are in good agreement with the measurements. Furthermore, how the parasitics change with the parasitic element values are investigated. The method only needs reflection coefficient of laser diode to be measured, which is simple because of the developed electrical‐domain measurement techniques. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1–4, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22987

Direct measurement of the polarization-dependent absorption and saturation in an InGaAs/InGaAsP single quantum well

A simple technique has been used to measure the two polarization-dependent absorption edges in a single quantum well around 1.5 μm. The broadband spontaneous emission of an AR-coated semiconductor laser chip was used as the spatially coherent light source in conjunction with a grating spectrometer. Absorption edges for both TE and TM polarized light have been measured in single quantum well InGaAs/InGaAsP waveguides and modeled by the k⋅p method. By pumping the devices with a 1.3 μm semiconductor laser, absorption saturation was also studied. The resulting changes in the refractive index were calculated from a Kramers–Kronig transformation of the absorption changes.

Wavelength stable uncooled fibre grating semiconductor laser for use in an all optical WDM access network

The use of angled facet semiconductor laser chips in fibre grating lasers (FGL) is shown to dramatically improve device characteristics over conventional normal facet FGLs. This improvement in performance allows the laser to be operated with no temperature control at 155 Mbit/s and makes it feasible for it to be used as a wavelength stable, uncooled source in a WDM optical access network.

Estimation of strain arising from the assembling process and influence of assembling materials on performance of laser diodes

A method for estimating strain in a semiconductor laser chip arising from bonding to foreign materials. The method is based on measurements of dependence of lasing wavelengths on duty ratios of pulsed operation with a constant peak current. The wavelength at zero duty ratio (λ0) is extrapolated from this dependence, from which the strain is estimated. Estimated strain from this method is in good agreement with result obtained from the change of polarization ratio, transverse-magnetic to transverse-electric light outputs. The strain arising from packaging affects not only lasing wavelength but also operating characteristics such as threshold current. Moreover, thermal resistance of laser diodes can be obtained from this dependence of lasing wavelengths on duty ratios.

Active mode locking of an erbium-doped fiber laser using an intracavity laser diode device

A ridge waveguide, GaInAsP semiconductor laser chip has been used intracavity as a loss modulator in an erbium-doped fiber laser. Operating at modulation rates of around 500 MHz, typical pulse durations of 40 ps were obtained, with average output powers of up to 10 mW. >