Johannes Sturm

Optical anisotropy in thin films of a blue electroluminescent conjugated polymer

We determined the anisotropic optical constants of thin films of a conjugated polymer, the methyl-substituted ladder-type poly(paraphenylene) (m-LPPP), over a large spectral range between 1.55 and 3.5 eV. In the subgap region the anisotropic refractive indices were obtained via waveguiding experiments at 1.55 eV and 1.95 eV. Propagation loss measurements revealed that the absorption coefficient parallel to the polymer film surface is very small (<12.6 cm−1) in this energy region, due to the high purity of the polymer. In the strongly absorbing energy region of the π–π* electronic transition (2.6–3.5 eV) we performed spectroscopic ellipsometric measurements, in order to determine the anisotropic optical constants parallel (No) and perpendicular (Ne) to the polymer surface. The optical anisotropy in the m-LPPP films can be attributed to a preferential orientation of the polymer chains in the plane of the substrate.

0.6–3-GHz Wideband Receiver RF Front-End With a Feedforward Noise and Distortion Cancellation Resistive-Feedback LNA

A novel wideband receiver RF front-end, including a resistive negative feedback wideband low-noise amplifier (LNA) with feedforward noise and distortion cancellation and a current commutating down conversion passive mixer with biquad trans-impedance amplifier, is presented in this paper. In comparison to conventional resistive negative feedback LNAs, theory analysis and experimental results for the proposed LNA circuit shows improved performance parameters, including voltage gain, noise figure (NF), and input-referred third-order intercept point (IIP3), especially helpful for wideband LNA design in modern deep-submicrometer CMOS. A wideband receiver RF front-end fabricated in 0.13-μm CMOS, based on the proposed feedforward noise and distortion-cancellation resistive-feedback LNA, has 42-48-dB conversion gain with 0.8-12-MHz tunable IF -3-dB bandwidth and 12-dB adjacent channel selectivity at 2 fp, -14-dBm IIP3, and 3-dB NF double-sideband with 10-kHz flicker-noise corner frequency.

A 0.1–4GHz resistive feedback LNA with feedforward noise and distortion cancelation

A novel resistive negative feedback wideband low-noise amplifier (LNA) with feedforward noise and distortion cancelation is presented in this paper. In comparison to conventional resistive negative feedback LNAs the proposed LNA circuit shows improved performance parameters including voltage gain, noise figure (NF) and input-referred third-order intercept point (IIP3). Especially for wideband LNA designs in deep sub-micrometer CMOS technologies, the proposed noise cancelation is efficient. A testchip is fabricated in 65nm CMOS. Measurement results show an LNA performance of 24dB voltage gain, 2dB NF, −5.5dBm IIP3 and S11<−10dB over 0.1–4GHz frequency range. The circuit consumes 12mW and the core layout size is 150μm×80μm.

Optical Receiver IC for CD/DVD/Blue-Laser Application

An optoelectronic receiver IC for optical data storage applications is presented. The IC was developed in a 0.5 /spl mu/m BiCMOS technology with integrated PIN-photodiodes. It includes a new architecture of high-speed and low-noise transimpedance amplifiers with a gain range of 130 /spl Omega/ to 270 k/spl Omega/ programmable with a serial interface. The bandwidth is 260 MHz for highest gain which gives a gain-bandwidth-product of 70 THz/spl Omega/ and a sensitivity improvement by a factor of 2 compared to published OEICs. The amplifiers support a special write/clip mode. The output buffers are 130 /spl Omega/ impedance matched for optimized data transmission over a flex cable.

A programmable OEIC for laser applications in the range from 405nm to 780nm

An OEIC with integrated PIN photodiodes for optical receiver applications like CD, DVD, HDDVD or Blu-ray, is presented. For the fast channels a maximum transimpedance of 465k/spl Omega/ or a sensitivity of 116mV//spl mu/W for 405nm with a bandwidth of 145MHz was achieved. The power consumption of 162.5mW at 5V is low enough for implementation in optical pickup units.

Vibrational analysis of derivatives of polyparaphenylene

Abstract Some new conjugated polymers are the subject of extensive studies since one found their ability to be used in the fabrication of light emitting diodes. For a purpose of optimization of such materials, a good knowledge of their electronic properties is essential. Therefore, we have studied their optical properties by means of vibrational techniques. In this paper, we report on two derivatives of Polyparaphenylene : one is an alkyl chain substituted PPP and the other is a deuterated ladder polymer, which has a planar conformation. Both are soluble because of alkyl substitution on phenyl rings. We present off-resonance Raman spectra of both compounds in solid state and assign the different modes with the help of dynamical calculations based on a valence force field model. The force constants of the phenyl rings have been taken from calculations performed on PPP and a good agreement is obtained between calculated and experimental data.

Integrated photodiodes in standard BiCMOS technology

Photodiode structures were integrated in a low cost 0.5 μm silicon BiCMOS process using standard process flow without any technology modification. Rise times of 1.3ns and 1.4ns were measured for wavelengths λ of 660nm and 780nm with a responsivity of 0.23 A/W and 0.14 A/W, respectively. Photodiodes with a high responsivity of 0.42 A/W are reaching a risetime of 4ns for λ = 780nm. Comparable low values for the risetime at 780nm are reported in the literature for integrated photodiodes in standard silicon technologies only with a modification of the epitaxial substrate material. So this photodiodes are suitable for a wide variety of low-cost high-speed optical sensor applications, for optical fiber communication and fiber in home applications.

Filter-less color sensor in standard CMOS technology

An integrated color detector is presented, which is implemented in a standard 130 nm CMOS technology without process modification or additional optical components like color filters. The proposed structure consists of vertically and laterally arranged photodiodes, providing color separation based on lateral carrier diffusion and wavelength-dependent absorption-depth. Three independent detector output signals with optimized spectral responsivities allows a discrimination between red, green and blue light spectral components. Linear transformation can be used to realize standardized colorimetric R, G, B or X, Y, Z color space responses. The color detector is therefore a low cost alternative solution for various color sensing applications.

Optical receiver IC for CD/DVD/blue-laser application

In this paper, an optoelectronic receiver IC for optical data storage applications is presented. The IC was developed in a 0.5 /spl mu/m BiCMOS technology with integrated PIN-photodiodes. It includes a new architecture of high-speed and low-noise transimpedance amplifiers with a gain range of 130 /spl Omega/ to 270 k/spl Omega/ programmable with a serial interface. The bandwidth is 260 MHz for highest gain which gives a gain-bandwidth-product of 70 THz/spl Omega/ and a sensitivity improvement by a factor of 2 compared to published OEICs. The amplifiers support a special write/clip mode. The output buffers are 130 /spl Omega/ impedance matched for optimized data transmission over a flex cable.

CMOS noise canceling balun LNA with tunable bandpass from 4.6 GHz to 5.8 GHz

A compact resistive-feedback low-noise amplifier (LNA) with single-ended input and differential output for multi-standard wireless receivers up to 6 GHz is presented. To relax external RF filters and LNA linearity requirements, an on-chip LC bandpass load is included with a continuously tunable center frequency from 4.6 GHz to 5.8 GHz. The LNA is implemented in 65 nm CMOS technology and achieves a measured gain up to 30 dB and an IIP3 linearity between -6.5 dbm and -10.3 dBm. Due to noise cancelation techniques the noise figure (NF) reaches a low value of 1.6 dB in the band of interest. The power consumption is below 16 mW at 1.2 V single supply. The active chip area is 154 μm * 197 μm. Therefore the proposed LNA structure is a cost-effective alternative to source-degeneration based narrowband LNAs with comparable performance. Since wide-band input impedance matching is employed, the LNA can be used in reconfigurable multi-standard wireless applications.