Bw Bauke Tilma

Design, Fabrication and Characterization of an InP-Based Tunable Integrated Optical Pulse Shaper

In this paper a tunable integrated semiconductor optical pulse shaper is presented. The device consists of a pair of arrayed waveguide gratings with an array of electrooptical phase modulators in between. It has been fabricated in InP-InGaAsP material for operation at wavelengths around 1.55 mum. Multimode inputs to the waveguide gratings are used to flatten their optical passband. We have used a new short-pulse characterization technique to fully characterize pulse shaping by the device, i.e., both the power and the phase profile. A fourfold decrease in pulse ringing was observed for the devices with flattened passbands. Moreover these devices showed a 25% increase in pulse peak power. The possibilities for using the device as a dispersion (pre-) compensator have been investigated. Pulse reconstruction could be obtained for dispersion values of up to 0.2 ps/nm. The fabrication technology of the pulse shaper is compatible with the fabrication of integrated mode-locked lasers, which makes further integration of complete arbitrary pulse generators possible.

Integrated Tunable Quantum-Dot Laser for Optical Coherence Tomography in the 1.7

In this paper, we present the design and characterization of a monolithically integrated tunable laser for optical coherence tomography in medicine. This laser is the first monolithic photonic integrated circuit containing quantum-dot amplifiers, phase modulators, and passive components. We demonstrate electro-optical tuning capabilities over 60 nm between 1685 and 1745 nm, which is the largest tuning range demonstrated for an arrayed waveguide grating controlled tunable laser. Furthermore, it demonstrates that the active-passive integration technology designed for the 1550 nm telecom wavelength region can also be used in the 1600-1800 nm region. The tunable laser has a 0.11 nm effective linewidth and an approximately 0.1 mW output power. Scanning capabilities of the laser are demonstrated in a free space Michelson interferometer setup where the laser is scanned over the 60 nm in 4000 steps with a 500 Hz scan frequency. Switching between two wavelengths within this 60 nm range is demonstrated to be possible within 500 ns.

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In this paper, we present the design, fabrication, and characterization of two monolithically InP-based integrated electro-optically tunable filters. The combination of these filters can be used to achieve a filter with a narrow passband and a large free spectral range. These filters are designed to be used in an integrated tunable laser source in the 1600-1800 nm wavelength region using active-passive integration technology. The fact that these filters worked successfully shows that this integration technology, originally designed to be used around 1550 nm wavelength, can also be used successfully in the 1600-1800 nm wavelength region without a large penalty in performance. The two filters, a high-resolution arrayed waveguide grating-type filters and a low-resolution multimode interferometer-tree-type filter are made tunable using 5 mm long electro-optic phase modulators in the arms of the waveguide arrays. Measurements show that these filters can be tuned over a wavelength range of more than 100 nm with an accuracy of 0.1 nm (1% of the free spectral range) for the high-resolution filter and an accuracy of 9 nm (4% of the free spectral range) for the low-resolution filter.

Wavelength Region

In this paper a study of waveguide photodetectors based on InAs/InP(100) quantum dot (QD) active material are presented for the first time. These detectors are fabricated using the layer stack of semiconductor optical amplifiers (SOAs) and are compatible with the active-passive integration technology. We investigated dark current, responsivity as well as spectral response and bandwidth of the detectors. It is demonstrated that the devices meet the requirements for swept-source optical coherent tomography (SS-OCT) around 1.7 μm. A rate equation model for QD-SOAs was modified and applied to the results to understand the dynamics of the devices. The model showed a good match to the measurements in the 1.6 to 1.8 μm wavelength range by fitting only one of the carrier escape rates. An equivalent circuit model was used to determine the capacitances which dominated the electrical bandwidth.

InP-Based Monolithically Integrated Tunable Wavelength Filters in the 1.6–1.8

We have realized a set of electro-optically controlled tunable arrayed waveguide gratings and present wavelength dependent calibration results for its tuning. These filters are designed to be used in a monolithically integrated tunable laser.

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We have designed and fabricated integrated dual-wavelength lasers in which an array waveguide grating is used as intra-cavity filter to allow lasing on two wavelengths within a common amplifier of the device.

m Wavelength Region for Tunable Laser Purposes

In this contribution we present a control method and its experimental verification for a laser which wavelength is controlled using tunable arrayed waveguide gratings (AWGs). This device has been fabricated monolithically on a single InP chip. The 35 mm-long ring laser cavity contains two tunable intra-cavity AWGs and two strained InGaAs quantum well (QW) optical amplifiers with optical gain around 1.7 μm wavelength. The components are connected using passive waveguides. The tunable AWGs are controlled by electro-optic voltage-controlled phase modulators (PHMs) in the arms of the waveguide array. These PHMs need to be controlled individually to tune the laser to a specific wavelength. The layout of the laser is depicted in Fig. 1(a). It is identical to a quantum dot (QD) based laser reported in [1].

InAs/InP(100) quantum dot waveguide photodetectors for swept-source optical coherence tomography around 1.7 µm

We have designed and fabricated a monolithically integrated continuously tunable laser source for frequency domain optical coherence tomography (FD-OCT) in the 1.6 to 1.8µm wavelength region. The InP-based laser consists of two 8mm long quantum dot (QD) semiconductor optical amplifiers and two electro-optically (EO) tunable filters in a 43.5 mm long ring laser cavity. An 8mm long output amplifier is used to boost the output signal. A picture of the mask is given in Fig. 1a.

Integrated tunable optical filters on InP for continuously tunable lasers

The application of the wavelength range of 1600 nm to 1800nm in optical coherent tomography (OCT) is attractive for its deeper penetration through the tissue due to a reduction of scattering [1]. One of the important elements in the OCT setup is the photodetector. The performance of commercial standard InGaAs detectors is limited due to low response for wavelengths above 1600 nm and p-doped InGaAs detectors have a significantly higher noise level. Thus a low noise photodetector working efficiently in this wavelength region is desired. In this contribution, we present our first results on quantum-dot (QD) waveguide photodetectors, which are realized by applying a reverse-bias voltage on a quantum dot semiconductor optical amplifier (QDSOA).

Integrated dual-wavelength semiconductor laser systems for millimeter wave generation

In this paper we report on monolithic laser devices that use InAs/InP (100) quantum dot gain material for optical amplifiers. The gain material has specific properties that can be exploited. It can provide a wide gain bandwidth around a wavelength that can be tuned with current density. In passive and hybrid modelocked lasers characteristic laser dynamics are observed. Such lasers can produced extremely chirped output as well as synchronised pulsed output on multiple wavelengths. Examples of such devices are presented and possible applications in pulsed and tunable lasers are discussed.