This article presents work on a Silicon-On-Insulator (SOI) compact sensing platform based on Micro Ring Resonators
(MRRs). In order to enable correction for variations in environmental conditions (temperature, mechanical stress etc), a
study has been performed on the performance of uncoated sensing MRRs, and of SU8- and SiO<sub>2</sub>-covered reference
MRRs. Excellent shielding for both cover materials has been obtained, however, water permeation into the SU8 causes a
slow drift in sensor response. We believe that a user-friendly, low-cost and robust way for optical interfacing to MRR
sensor chips is required for practical application in Point-Of-Care diagnostics, and that the cost and complexity of
optical-electrical read-out systems must decrease. We have taken first steps to realize that vision, by building a prototype
free-space optical coupling set-up, which enables non-photonic experts to characterize surface activation processes using
MRRs. Moreover, we present our first steps towards on-chip read-out systems.
ePIXfab-The European Silicon Photonics Support Center continues to provide state-of-the-art silicon photonics solutions to academia and industry for prototyping and research. ePIXfab is a consortium of EU research centers providing diverse expertise in the silicon photonics food chain, from training users in designing silicon photonics chips to fiber pigtailed chips. While ePIXfab provides world-wide users access to advanced silicon photonics it also focuses its attention to expanding the silicon photonics infrastructure through a network of design houses, access partners and industrial collaborations.
We demonstrate all-optical NOR logic operation of four data signals in one SOA. Exploiting XGM, wavelength
multiplexing and optical filtering for signal discrimination, we purpose an implementation in which an all-one optical
probe signal is modulated by the optical sum of four different data signals at 10 Gbps each. Data signals act as pump and
reduce the gain of the SOA producing on-off keying of the probe and, hence, the NOR behavior. We derive the
feasibility of a multiple-bit NOR from a simple XGM setup working at a wide range of pump power by means of a
characterization with all-one RZ streams. High-resolution measures of the signals are presented to illustrate nonlinear
effects and wavelength management. Signals traces are showed to prove logic functioning and 4-bit gate quality is
reported by means of eye diagrams of the output signal for different input powers.
In this paper we report the design, fabrication, simulation and characterization of a novel discretely
tunable laser based on filtered feedback. This Integrated Filtered-Feedback Tunable Laser (IFF-TL) device
combines a simple and robust switching algorithm with good wavelength stability. It consists of a Fabry-Perot
laser with deeply-etched broadband DBR mirrors. Single mode operation is achieved by using feedback from an
integrated filter. This filter contains an AWG wavelength router and an SOA gate array. A rate equation model
predicts that a properly designed device can switch within 1 ns, while characterization measurements show a
value of only 4 ns. The fast switching and reduced control complexity makes the device very promising for various
advanced applications in optical telecommunication networks.
The constraints on dilute-nitride Semiconductor Optical Amplifiers (SOAs) for multi-wavelength amplification have
been evaluated. SOAs have been fabricated by angling the facets of a GaInNAs/GaAs edge emitting laser using gas
enhanced focused ion beam etching. The original laser has been characterized in terms of its temperature dependence and
net modal gain. A full width half maximum (FWHM) of 40nm has been found at 298K. Good temperature stability has
also been found with a value of 0.35nm/K for the lasing wavelength. The good temperature stability of the device has
been explained in terms of the role that the monomolecular recombination plays in the temperature dependence of the
device. The monomolecular recombination has been reported temperature independent having two key effects; reduction
of the temperature performance and reduction of the dynamic performance in terms of an increase in the threshold
current and a decrease of the high speed potential. Iodine gas enhanced focused ion beam etching (GAE-FIB) has been
used for the fabrication of the SOA, the iodine gas increasing the etching rate by a factor of 2.5. The fabrication has been
completed in two steps; in the first one the facets have been angled and in the second step a cross-section procedure has
been employed for smoothing of the facets. Once the SOA has been fabricated its potential for simultaneous multiple
channel amplification has been studied. A flat gain spectrum over a range of 40nm has been obtained. This value and the
wavelength range have good agreement with the net modal gain measured in the original laser device. In addition,
minimum channel interspacing has been achieved with no wavelength degradation.
At the present time, there is a considerable demand for long wavelength (1.3μm-1.5μm) laser diodes for low cost data-communication applications capable of operating at high speed and at high ambient temperatures without the need for thermoelectric coolers. First proposed in 1995 by M. Kondow, the GaInNAs/GaAs material system has attracted a great deal of interest as it promises good temperature performance. The broad gain observed in GaInNAs/GaAs QW samples suggests that wavelength tuning should be possible by the application of gratings to select an optical mode. In addition, splitting the contact has been shown to improve modulation speed in other materials. These two methods should be able to be used jointly and processed together. The use of split-contact lasers has the advantage of that no change is made in the processing steps, since there is only need for a new metal mask to define a new top p-contact. Despite the bandwidth enhancement of two-contact lasers compared to the single contact case is well known, to the authors' knowledge, so far it has not being applied to GaInNAs/GaAs lasers. The use of Bragg-gratings on the ridge waveguide of the laser will generate a periodic modulation inducing an interaction between the forward and backward travelling modes. The effect of this interaction is the one of a band pass filter on the gain shape of the laser, allowing filtering out the actual lasing wavelength, and tuning the lasing wavelength in the range of wavelengths with substantial optical gain. Therefore, this method can be used optimally in lasers with broad gain, as is the case of GaInNAs/GaAs. In this paper, we reveal experimental investigations in how to apply these two post-processing methods to 600m-long 1.25μm-Ga<sub>0</sub>.66In<sub>0</sub>.34N<sub>0</sub>.01As0.<sub>0</sub>.99/GaAs 6nm single quantum-well ridge waveguide lasers.
The potential of 1.3um GaInNAs SQW laser diodes for high speed operation is experimentally investigated in this paper, computing the differential gain, dg/dn, at a temperature range suitable for most network applications (293K-348K) and the small signal modulation bandwidth. The investigation begins with a basic characterization calculating the T0, with a value of 56K in a range of temperatures of 293K-318K. The lasing wavelength at 293K is found to be 1250nm with a linear temperature dependence of 0.377nm/K. Secondly, the paper presents a detailed study of the modulation bandwidth of the device, obtaining a value of 6.06Ghz for the maximum modulation bandwidth at 293K. In a range of temperatures of 293K-318K, the modulation bandwidth is found to decrease only slightly with the temperature with a slope of 0.0088Ghz/K. Finally, the paper explains the temperature behaviour obtained for the modulation bandwidth studying the temperature dependence of the differential gain, dg/dn. For this evaluation, the value of the differential gain with the current (how the peak gain changes with the sub-threshold bias current applied to the sample), dg/dI, is obtained using the Hakki-Paoli method. Using impedance measurements, a relation between the carrier density, n, and the bias current applied to the laser, I, has been obtained. With this relation, we obtained the differential current with the carrier density, dI/dn. Then, we calculated the differential gain dg/dn = dg/dI * dI/dn. To conclude we saw how the differential gain, dg/dn, has been found to have similar temperature behaviour as the small signal modulation bandwidth.
GaInNAs quantum well lasers have attracted significant interest in recent years. Their potential for operation at high temperatures without coolers and their application for low cost vertical-cavity surface-emitting lasers (VCSELs) are the main reasons for this interest. The main consequence of adding Nitrogen (N) to InGaAs materials is the band gap shrinkage. The reason for that is the interaction of N (acting as a localized defect) with the conduction band of the InGaAs. In previous studies, low temperature PL measurements of the impact of Nitrogen on the band structure of GaIn NAs have been examined. Pulsed measurements using a broad area GaInNAs QW laser were carried out and the results were analyzed in terms of the interaction of the N defect state with the GaInAs conduction band edge (band-anticrossing model). A detailed experimental temperature study of single quantum-well GaInNAs lasers at room temperature and above has been carried out. Experimental results of L-I, T<sub>0</sub>, temperature dependence of lasing wavelength, optical gain and efficiencies are presented, discussed and compared with other materials. The temperature ranges studied is appropriate for most network applications. The gain spectra for moderate densities were experimentally measured using the method of Hakki and Paoli: the 600 μm long devise is biased below threshold and the gain is evaluated form the Fabry Perot modulation of the spontaneous emission spectra. A new concept will be introduced to study the bandwidth of the spectral gain and see its dependence with the temperature. The half-peak-BW will be the bandwidth where the gain decreases 50% from the peak gain. The temperature performance of the half-peak-BW has been studied obtaining a slope of 0.5871 nm/K. About the temperature dependence of the laser, a value of T<sub>o</sub> (50 K) similar than the one found in InGaAsP has been found. This might disagree with the first results published of this new material system, giving extremely high values above 100 K. This is due to the high A parameter found in the previous materials. The improvement of the material is decreasing the A parameter and the characteristic temperature of the device. A small temperature dependence of the lasing wavelength was found (0.37 nm/K). This value was confirmed measuring the temperature dependence of the gain peak wavelength. This small temperature dependence can be understood by the interaction of the N state with the conduction band edge.