We present finite difference thermal modeling to predict temperature distribution, heat flux, and thermal resistance inside lasers with different waveguide geometries. We provide a quantitative experimental and theoretical comparison of the thermal behavior of shallow-ridge (SR) and buried-heterostructure (BH) lasers. We investigate the influence of a split heat source to describe p-layer Joule heating and nonradiative energy loss in the active layer and the heat-sinking from top as well as bottom when quantifying thermal impedance. From both measured values and numerical modeling we can quantify the thermal resistance for BH lasers and SR lasers, showing an improved thermal performance from 50K/W to 30K/W for otherwise equivalent BH laser designs.
We report on our recent advances on integrated hybrid InP/SOI transmitters using the Silicon Photonic fabrication technology. We demonstrate the direct modulation at 10 Gbits/s of different laser configurations such as wavelength tunable lasers, Distributed FeedBack (DFB) lasers and Chirp Managed Lasers (CMLs). We will also present the design, fabrication and characterization of various hybrid InP/SOI transmitters integrating lasers (tunable or DFB) and modulators (silicon or III-V) with modulation up to 32 Gbits/s.
Silicon photonics has reached a considerable level of maturity, and the complexity of photonic integrated circuits (PIC) is steadily increasing. As the number of components in a PIC grows, loss management becomes more and more important. Integrated semiconductor optical amplifiers (SOA) will be crucial components in future photonic systems for loss compensation. In addition, there are specific applications, where SOAs can play a key role beyond mere loss compensation, such as modulated reflective SOAs in carrier distributed passive optical networks or optical gates in packet switching. It is, therefore, highly desirable to find a generic integration platform that includes the possibility of integrating SOAs on silicon. Various methods are currently being developed to integrate light emitters on silicon-on-insulator (SOI) waveguide circuits. Many of them use III-V materials for the hybrid integration on SOI. Various types of lasers have been demonstrated by several groups around the globe. In some of the integration approaches, SOAs can be implemented using essentially the same technology as for lasers. In this paper we will focus on SOA devices based on a hybrid integration approach where III-V material is bonded on SOI and a vertical optical mode transfer is used to couple light between SOI waveguides and guides formed in bonded III-V semiconductor layers. In contrast to evanescent coupling schemes, this mode transfer allows for a higher confinement factor in the gain material and thus for efficient light amplification over short propagation distances. We will outline the fabrication process of our hybrid components and present some of the most interesting results from a fabricated and packaged hybrid SOA.
F. Lelarge, R. Brenot, B. Rousseau, F. Martin, G. Patriarche, F. Poingt, L. LeGouezigou, O. Le Gouezigou, C. Dernazaretian, E. Derouin, O. Drisse, F. Pommereau, A. Accard, M. Caligaro, D. Make, J.-G. Provost, P. Resneau, B. Dagens, F. van-Dijk, M. Krakowski, G. H. Duan
We report on the recent advances in InP-based Quantum Dashes (Qdashes) material for 1.55μm optoelectronic devices.
We achieve highly uniform, reproducible and wavelength-controlled Qdashes, with a length ranging from 50nm to
500nm depending on the growth conditions. These Qdashes lead either to high modal gain distributed feedback (DFB)
lasers or low chirp semiconductor optical amplifier (SOA). Moreover, we demonstrate that Qdashes are compatible with
buried ridge stripe and shallow ridge technology and lead to very reliable lasers. Directly modulated lasers with 10GHz
bandwidth are demonstrated in continuous wave mode operation. 10Gb/s transmission over 25km in semi-cooled
operation is achieved using DFB buried lasers. Qdashes optimization leads to SOA with internal gain of 10 dB and a -3dB optical bandwidth of 120 nm at 50°C, paving the way for semi-cooled CWDM optical sources. Furthermore, low
chirp Qdashes SOA are evaluated as optical boosters after a modulated source. Although we still observe overshoots on
the amplified signal, the chirp, even in their saturation regime, is low enough to allow for 50 km of transmission at
10Gb/s.
Guang-Hua Duan, F. Lelarge, B. Dagens, R. Brenot, A. Accard, A. Shen, F. van Dijk, D. Make, O. Le Gouezigou, L. Le Gouezigou, J.-G. Provost, F. Poingt, J. Landreau, O. Drisse, E. Derouin, B. Rousseau, F. Pommereau
This paper summarizes recent advances on InAs/InP mode-locked quantum dashes (QD) lasers, and their applications for
all-optical clock recovery, short pulse generation and millimeter wave generation. We demonstrate that QD FP lasers,
owing to the small confinement factor and the 3D quantification of electronic energy levels, exhibit a beating linewidth
as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the
excellent phase noise and time jitter characteristics when QD lasers are actively mode-locked. We report also on an
actively mode-locking tunnel injection quantum dash Fabry-Perot laser diode at 42.7GHz, generating nearly Fourier
transform limited pulses with a pulse width of 2ps over 16nm.
The unique optical properties of photonic crystals allow a dense and simple integration of optical functionality on a
small footprint. We have investigated the integration of tunable photonic crystal (PhC) lasers with a wavelength monitor.
The small size of the monitor allows an integration on an all-active layer structure, which leads to a rather simple
fabrication process. The tunable lasers are based on two coupled PhC waveguides with slightly different length. PhC
mirrors are placed at the end, joint and front of the two waveguides. Tuning is achieved by a variation of the injection
currents in the two segments. The wavelength monitor, which is placed behind the rear mirror of the laser, consists of a
multi-mode PhC waveguide. Mode coupling between the fundamental mode and a higher order mode results in a
wavelength-dependent transmission of the waveguide. In the region of the mode coupling, the higher order mode is
extracted out of the waveguide through a sufficiently thin waveguide boundary. The power of the transmitted and
extracted light is detected by two photodiodes, which are integrated with the wavelength monitor. The photocurrents of
the these diodes show a clear dependence on the laser wavelength, in good agreement with simulations.
Quantum dot (QD) materials offer attractive performances for the development of lasers and amplifiers at 1.55μm. The
3-D quantification of the energy levels in QD leads to several advantages, such as high optical gain and efficiency, low
sensitivity to temperature variations, low noise and low linewidth enhancement factor. We shall present in this paper the
growth and basic properties of QD materials for lasers and amplifiers, and device performances with particular interest
for optical communications and microwave transmission.
Real-time monitoring by multiwavelength phase modulated ellipsometry (PME) of the growth of plasma deposited microcrystalline Silicon ((mu) c-Si) is presented. Several growth models for process-monitoring are reviewed, and in particular the inhomogeneity in the (mu) c-Si layer is treated by allowing graded-index profile in the bulk. By also using the Bruggeman effective medium theory to describe the optical properties of (mu) c-Si, the monitoring of the crystallinity in the upper and lower part of the layer, together with the thickness is demonstrated. The inversion algorithms is very fast, with calculation times within 5 seconds using a standard Pentium computer. This opens up for precise control of surface roughness, bulk thickness, and crystallization of both the top and bottom interfaces of the layer during the elaboration of devices such as solar cells and thin film transistors.
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