Nam Gutzeit

Geometrical tolerance of optical fiber and laser diode for passive alignment using LTCC technology

The upsurge in the demand for high capacity communication links results in a rapid growth in the field of optical fiber communication. Recent advances in satellite communications urge for the transmission of high-frequency signals with minimal losses, and it is regarded that radio-over-fiber is the solution for such broadband analog applications. Considering the many advantages offered by low-temperature co-fired ceramics multilayer technology, it is promising to use this technology for passive alignment of an optical fiber to a laser diode, eventually hybrid-integrated with an electro-optical modulator for microwave frequencies. In this paper, we analyzed the necessity of efficient coupling of optical power into the fiber in an optical link, based on intensity modulation and direct detection. We also estimated the alignment tolerance as +/-20 μm, which can be realized exploiting recent advances of the ceramic multilayer technology.

High resolution patterning of LTCC based microwave structures for Q/V-band satellite applications

Highly substrate integrated microwave circuits for space applications require a high metal pattern accuracy for transmission line structures and components. Within this work an embedded 60 GHz strip line filter is used as a demonstrator device to compare four fine line structuring processes for multilayer Low Temperature Cofired Ceramics (LTCC). Fine line screen printing (type I), resinate thin film patterning (type II), laser patterning in green state (type III) and laser patterning of fired screen printed thick films (type IV) are compared regarding pattern tolerances, electrical performance and process implementation capability. All substrates were manufactured using a subsequent tape-on-substrate process (ToS) to embed the filter. The filter measurements exhibit an insertion loss of 4 dB at centre frequencies of nearly 60 GHz for all variations.

High Resolution LTCC Laser Processing in the Green and Fired State for Future Technologies

Abstract In this publication the results of laser structuring processes of LTCC substrates, screen printed and laser structured gold thick film lines and the processing procedures are presented. To investigate the compatibility of the laser processes into the conventional LTCC process chain the laser structuring was done in green as well as in fired state. Typical easy electrical patterns like miniaturized interdigital structures and meanders serve as examples of the reached resolution and geometrical borders of the laser structuring techniques at the Center of Micro- and Nanotechnologies of the TU Ilmenau (IMN Macro Nano®). The lateral precision and the topological shape are determined by laser scanning microscopy. The aimed structures have lines and spaces of 30 μm. A statistical evaluation is done to show the possibilities and the limits of the new laser structuring processes with picosecond UV laser ablation systems.

Passive alignment of an optical fiber on a multi-layer ceramic module for radio-over-fiber applications

The low-temperature co-fired ceramics technology is a successful and space-qualified technology enabling three-dimensional microwave design. Now we are pursuing an important step further towards multi-functional multi-purpose hybrid assembly technologies: combining ceramic technology with optical fiber technology. In such systems, fiber alignment is a crucial issue. Extra gadgets used for the fiber alignment make the system more complex and bulky. Considering the many features offered by the ceramic multi-layer technology for size reduction, it is advantageous to use this technology for the passive alignment of an optical fiber above the optical source. In this paper, the passive fiber alignment employing flip-chip mounting of a vertical cavity surface emitting laser in a ceramic substrate is presented. We have studied the performance of the resulting optical link with respect to figures typical for radio-over-fiber applications, namely the link gain, noise figure, and the spurious-free dynamic range and compared the results with a link where the VCSEL was wire bonded to the circuit.

Optimized cavities for microwave applications using the new low loss LTCC material Du Pont 9k7

This paper presents two different novel methods to manufacture optimized cavity structures, which are suitable for multilayer System-in-Package (SiP) and Multi-Chip-Module (MCM) applications, in the new low temperature cofired ceramic (LTCC) material Du Pont 9k7. In contrast to standard manufacturing, the improved DP 9k7 cavities show almost perfectly orthogonal cross sections and straight edges, achieved by applying special cavity inlays or cast silicone. Ball-wedge bond wires and wedge-wedge ribbons are implemented directly to the cavity rim successfully. Therefore, these cavities are suitable for very short bond wires in complex RF systems and the introduced techniques are very promising for future applications using DP 9k7.

Effect of internal silver conductor on heat spreading capability of LTCC membrane

LTCC membranes are used as substrates of screen printed unimorph deformable mirrors. A high piezoelectric stroke is attributed to thin substrate materials. The application of deformable mirrors with high laser loads calls for a large heat spreading capability of the deformable unimorph mirrors. A large heat spreading capability is attributed to high thermal conductivity of the materials that is not allocated by LTCC. The present paper reports on the effect of internal silver conductor (DuPont 6145) on the heat spreading capability of the LTCC membrane. Therefore, internal silver conductor is applicated into a 570 μm thin membrane on a diameter of 49.8 mm. The optical absorption of plain LTCC membranes and membranes with internal metallization is characterized by an Ulbricht sphere. Membranes with internal silver conductor and a reference sample without internal metallization (plain LTCC) are loaded with a laser beam. The absorbed laser power heats the LTCC membrane. We investigate the temperature increase...