Designing photonic integrated circuits (PICs) with packaging in mind is important since this impacts the performance of the final product. In coherent optical communication applications there are a large number of DC and RF lines that need routed to connect the PIC to the outer packaging. These RF lines should be impedance matched to the devices, isolated from each other, low loss and protected against electromagnetic interference (EMI) over the frequency range of interest to achieve the performance required for the application. Multilevel low temperature co-fired ceramic (LTCC) boards can be used as a carrier board connecting the PIC to the packaging due to its good RF performance, machinability, compatibility with hermetic sealing, and ability to integrate drivers into the board. Flexibility with layer numbers enables additional layers for shielding against electromagnetic interference or increased space for routing electrical connections. In this paper the design, simulations, and measured results for a set of 4 phase matched transmission lines in LTCC that would be used with an IQ MZM are presented. The measured 3dB bandwidth for a set of four phase matched transmission lines for an IQ MZM was measured to be 19.8 GHz.
The packaging of high speed Photonic Integrated Circuits (PICs) should maintain the electrical signal integrity. The standard packaging of high speed PICs relies on wire bonds. This is not desirable because wire bonds degrade the quality of the electrical signal. The research presented in this paper proposes to replace wire bonds with an interposer with multilevel transmission lines. By attaching the PIC by flip chip onto the interposer, the use of wire bonds is avoided. The main concern for designing an interposer with multilevel transmission lines is the vertical transition, which must be designed to avoid return and radiation losses. In this paper, a novel design of a high speed vertical transition for Low Temperature Co-fired Ceramic (LTCC) is presented. The proposed vertical transition is simpler than others recently published in the literature, due to eliminating the need for additional ceramic layers or air cavities. A LTCC board was fabricated with several variations of the presented transition to find the optimal dimensions of the structure. The structures were fabricated then characterized and have a 3 dB bandwidth of 37 GHz and an open eye diagram at 44 Gbps. A full wave electromagnetic simulation is described and compared with good agreement to the measurements. The results suggest that an LTCC board with this design can be used for 40 Gbps per channel applications. Keywords: Photonics packaging, Low Temperature Co-Fired Ceramics.
To compensate for velocity mismatch in travelling wave opto-electronic devices, the microwave velocity of the propagating RF signal is reduced by introducing capacitively loaded elements. For high speed operation, these elements must be electrically isolated from one another, which is typically achieved by using ion-implantation to render the p-doped material non-conducting. We propose and demonstrate through optical and electrical simulations that ion-implantation can be avoided by using a quasi-shallow etch to electrically isolate the capacitive elements. High isolation can be achieved using such an etch without introducing additional losses to the propagating optical signal.
We present a study of the total internal reflection of a Helmholtz-Gauss beam at a plane interface between
two dielectric media. The derivation is based on the decomposition of the Helmholtz-Gauss beams in terms of
its constituent plane waves components. We determine the shift predicted by the classical theory of the Goos-
Hänchen shift and analyze the transverse intensity patterns of the reflected waves for a variety of Helmholtz-Gauss
beam including Bessel-Gauss and Cosine-Gauss beams.