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The design and performance of optical switches are crucial for switch-based beam steering devices to be competitive among existing beam steering technologies for light detection and ranging (LIDAR) applications. An efficient liquid crystal (LC) filled directional coupler (DC) optical switch is proposed. Device performance as a function of geometric design is analyzed through numerical simulations. The analysis reveals that the DC is a promising candidate to replace more popular Mach-Zehnder Interferometer (MZI) configurations for optical switches when ultra-low $\mathrm{V}_{\pi}\mathrm{L}$ performance is important.

We characterize the thermo-optic coefficient of silicon nitride films with varying silicon contents using plasma-enhanced chemical vapor deposition (PECVD). A clear relation between the silicon content and the exhibited thermo-optic coefficient has been demonstrated along with a coefficient as high as (1.65±0.08) ×10-4 K-1.

We describe a new class of electric motor/generator technology with specific power more than 10kW/kg for a variety of applications including terrestrial, airborne hybrid and all electric propulsion. The technology utilizes a new type of turn-less electro-mechanics configuration intimately integrated with dedicated inverters which utilize high current, low voltage GaN MOSFET switches.

In this paper, we review the key performance of optical modulators operating in the wavelength range of 1.3–1.5 μm for fiber-optic link applications and compare the design of two nanoscale modulators which are based upon (a) second-harmonic generation (SHG) from GaN nanopillars and (b) electrooptic polymer in nanoslot waveguides, respectively.

Second-harmonic generation (SHG) from single GaN nanpoillar is reported. A model for the SHG processes in the GaN nanopillar as a function of diameter is presented; the analysis showed quantitatively that the SHG is dominated by its surface area. The effective second order nonlinear optical susceptibility increases as the diameter of the GaN nanopillar decreases, reaching a value of 136 pm/V at 150nm diameter, making them attractive for modulator applications.

We studied the impact of optical pulse coding techniques on Brillouin optical time-domain analysis (BOTDA) systems experimentally. The results show that complementary-coding-based schemes can provide significant enhanced signal-to-noise ratio (SNR) to the BOTDA system. Using complementary coding, the average time can be reduced significantly and so does the measurement time. The complementary-coded pulses with individual pulse duration of 0.1 ns allowed us to realize temperature sensing over 50 m of single-mode fiber with 1-cm spatial resolution.

We study nanopatterned multilayer hyperbolic metamaterials with tunable plasmonic properties for enhancing fluorescent molecules and LEDs at different working wavelengths. About two order of magnitude of spontaneous emission rate enhancement was demonstrated.

High power photodiodes were proposed in prior works for conversion of broadband modulated optical signals to electrical signals for transmission at high frequencies. At moderate to high optical powers, the linearity of the photodiode becomes a main concern for achieving high linearity transmission in fiber link. In this invited talk the mode analysis for understanding the absorption profile of high power coupled waveguide photodiodes is presented. which also illuminated the design parameters pertinent for high saturation power and linear detection.

This paper presents results of normally-off AlGaN/GaN MOS-HEMTs fabricated with a two-step gate recess technique which includes a chloride based Inductively Coupled Plasma (ICP) etch followed by HCI and NH 4 OH surface treatment. The latter can effectively smoothen evenly the ICP etched surface. The two-step gate recessed device with atomic layer deposited (ALD) Al 2 O 3 as gate dielectric delivers a threshold voltage (V th ) of +1V and a maximum current density per gate width (I max ) of up to 0.583 A/mm which is 90% that of an un-recessed gate depletion-mode AlGaN/GaN HEMT device (V th of −3.5V) fabricated from the same epitaxial wafer.

The radio-over fiber (RoF) transmission is a promising method for broadband signal transmission over long distances. For intensity modulated broadband signals, the fiber dispersion accumulated over long fiber can lead to power fading of the signal. The power fading drawback can be largely alleviated when optical single-side-band (OSSB) modulation approach is adopted, which had been demonstrated via different optical filter schemes [1][2]. However, the majority of these past filtering approaches also introduce additional distortions due to the filter response. We have recently proposed and demonstrated a novel yet practical approach of cascading four identical off-the-shelf 100 GHz optical bandpass Fabry-Perot filters into a fiber link, which not only minimizes the power fading effect, but also increases Carrier-to-Noise ratio and maintains the distortions at a low level [3]. In this paper the distortions are further characterized and compared between links using single filter and cascaded filter respectively, which provides insight on how the cascaded filter maintains the linearity while mitigates the power fading.

In this paper, we propose and experimentally verify that optical filters with fast linear roll-off property, when incorporated in an optical transmitter, can minimize not only the fading effect commonly observed in high bit rate, long distance fiber links, but also improve the link Carrier-to-Noise ratio, and at the same time can maintain the 3rd order inter-modulation distortions at a relatively low level.

In this paper, we demonstrate the critical design considerations for GaN-based microwave power varactors for the purpose of achieving high breakdown voltage, high Q-factor and high linearity. The extraction of these parameters from a real GaN-based power varactor diode is also presented. High values of these parameters are obtained, which is critical for the applications in the wireless base-station communications.

Semiconductor varactors are receiving increasing attention because of their potential to provide adaptive and tunable characteristics for the front-end of wireless communication systems, enabling efficient multi-band and software-defined radios. For base-station applications, Q > 100, breakdown voltage > 100 V and OIP3 > 65 dBm are required. The combination of high Q and high-breakdown voltage requires semiconductors with high mobility and high-breakdown electric field [1]; GaN with a mobility of >∼ 500 cm2/Vsec and a breakdown electric field of 2.5 MV/cm is a promising candidate. SiC-based varactors have also been recently reported [2]. We have previously demonstrated GaN large-area varactors that achieve high-breakdown voltage. The addition of a thin InGaN surface layer was shown to increase the diode breakdown voltage and reduce the leakage current under high reverse bias [3]. In this work, InGaN/GaN Schottky-diode microwave varactors with Q > 100 at 1 GHz, breakdown voltage > 120 V and OIP3 > 71 dBm are reported. To the best of our knowledge, the combination of Q, voltage handling capability and OIP3 represents advancement from any other reported varactors.

Careful measurements of the OIP3 in high power photodetectors show a resonance peak at a particular bias voltage and photocurrent combination. In fact, for a given photocurrent, there exists an optimum bias voltage that maximizes the OIP3. One can envision a DC control circuit that would be able to maintain the optimum OIP3 performance from the photodiode. By optimizing the bias voltage for a given photocurrent, a peak OIP3 of +65dBm was measured which is believed to be the highest reported value to date.

The small size, light weight and low cost are main advantages of analog fiber links over coax links. In particular, analog fiber link is examined for photonic antenna (see Fig. 1) operating at high center frequencies in which a high power photodiode is deployed close to the antenna for downlink broadcasting [1]. High power and high output third order intercept point (OIP3) are among critical photodiode requirements in such application.

We have described a high optical power transmitter suitable for applications in harsh environments that require data modulation rates of up to 10 Gbps and modulated optical output power up to 25 mW. The compact package format enables size reductions for free space laser communications and antenna remoting terminals. High efficiency operation at lower optical power will provide DC power savings for digital transmission.

HPM systems fall into two general categories. The first uses moderately high power, quasi CW sources in the MW range with pulse duration around a millisecond and are generally of narrow bandwidth but with large average power. In the second category we have very high Peak power - in the GW range, but of very short pulse duration, typically in the 100ns range, and are of a large bandwidth. These sources, due to their pulse power technology are limited in average power and pulse repetition frequency. Some HPM applications require beam steering either by mechanical means or by phasing an array. Some applications, such as counter electronics, require the continuous sweeping of the beam over a large forward area. Sweeping arrays require phase shifters that are costly and difficult if they are required to accommodate a large bandwidth and Power.

Voltage-dependent responsivity nonlinearities are characterized experimentally and analytically for uni-traveling carrier directional coupled photodiodes (DCPD) with two types of design variations. OIP3 data follows the voltage-dependent responsivity predictions for both MMI width and PD width variations of the baseline DCPD. A maximum OIP3 of 39dBm was achieved for a device with a 3µm wide PD at 20mA and 4V.

A three laser two tone setup removes unwanted nonlinearities from the third order intercept point (IP3) measurement. A high frequency photodetector with an IP3 upwards of 30 dBm will be analyzed up to 18 GHz using the new setup and with the circuit model used in Jiang (2000).

Different wafer bonding techniques for heterogeneous integration are compared; in particular, the advantages and disadvantages of metal bonding using isothermal solidification (ITS) process are investigated. In applying the ITS metal bonding to Si and GaAs integrated circuits, two distinct approaches - pre-patterning and post-patterning, are developed and the resulting metal bond properties, such as electrical contact and thermal conductivities, are presented.

In consultation with the technical program committee of AVFOP 2007, we have scheduled a technical program for MWP 2007 that will provide flexibility to the attendees and the guest attendees of both conferences. MWP 2007 will begin with a workshop on photonic integration as enabler of economically-scalable applications of microwave photonics, and proceed with two days of oral and poster sessions. Of the 96 papers, including 11 invited talks, submitted to this year?s conference through the website, the committee accepted a total of 65 papers for either oral or poster presentation. The oral presentations have been grouped into sessions that will focus on topics of interest to the microwave photonics community, namely, advances in devices for analog links, radio-over-fiber technology and systems, microwave photonics signal processing, oscillators, optoelectronic integration, microwave photonic techniques for antennas and imaging, and techniques for coherent link and broadband transmission. The poster presentations are also grouped along these topics.

Peripheral coupled waveguide (PCW) electro-absorption modulator (EAM) with different dimensions is studied. By incorporating a waveguide taper in the PCW to reduce the absorption at the input facet of the EAM, we show that the saturation effect due to high current density can be reduced.

This study presents a novel model of a high-speed uni-travelling-carrier travelling wave (UTC-TW) photo detector for submillimeter wave signal generation. The model is fully analytical and is intended to be used as a design tool. This newly designed photo detector can operate well above 100 GHz.

This presentation gives an overview of the requirements of the photonic components in their insertion in applications such as CATV, antenna remoting and base station connections in wireless communication systems. While the driving force for their use is bandwidth, the eventual limiting factors would be cost and reliability. The presentation reviews the advances in the state-of-the-art photonics devices for analog links such as laser diodes, high power lasers, external modulators, semiconductor amplifiers, erbium doped fiber amplifier, and photodetectors. Comparisons will also be made regarding the direct modulation scheme versus the external modulation scheme. Research frontiers in external optical modulators will be described.

High speed photo detectors are very useful components for high capacity optical communication links, generation of MM and sub-MM wave signals and more. The most promising photo detector for speed is the UTC-TW PD, which was proposed a few years ago. Operation of such devices was reported at frequencies exceeding 300 GHz. Output power and efficiency improve as the optical power is increased, however, when the optical power exceeds the saturation level, substantial reduction is observed in bandwidth. In this paper we present experimental results demonstrating the bandwidth degradation at high optical power, and offer an explanation to this phenomenon, which is backed up by theoretical simulations.

The linearity and link gain performance of analog fiber-optic links based on electroabsorption modulators operating at high optical power is analyzed. The negative feedback attributed to the photocurrent generation improves the modulator linearity at high optical power while causes the link gain to saturate. Potential schemes to improve both will be presented.

We demonstrate the use of an area selective zinc indiffusion technique to fabricate an integrated InP Mach-Zehnder optical modulator. The modulator exhibits an extinction ratio of 19 dB and a voltage swing of plusmn2.3 volts at a wavelength of 1550 nm. The extinction ratio is only reduced to -18 dB when operated over a 40 nm range, with the center wavelength around 1560 nm. The Vpi voltage is increased from 4 volts at 1540 nm to 7.1 volts at 1580 nm. Very good electrical isolation is obtained between the contacts, which confirms the potential of the technique for the fabrication of photonic integrated circuits (PIC)

We demonstrate here a dual function electroabsorption waveguide device that operates as a modulator in the receiving mode and a detector in the transmitting mode in the case of antenna remoting application. Both electroabsorption modulator (EAM) and photodetector (PD) are known to saturate at high optical inputs as a result of space-charge carrier screening in the EAM modulating or PD absorbing depletion region as well as from the inadequate thermal power dissipation. Our device is designed to operate at high levels of incident input optical power. In the photodetector mode it sustained 590 mW of optical input power and generated 222 mA of output current. To our knowledge it is the highest current demonstrated for a single mode waveguide photodetector

In this paper the generation of sub-mm wave signals by heterodyning two optical signals in a photo detector is considered. Previous work exhibits very low power efficiency (

This presentation gives an overview of the requirements of optoelectronic links for their insertion in applications such as CATV, broadband wireless LAN and other sensing applications. In particular, the recent development of high power photodiodes for conversion of broadband modulated optical signals to electrical signals for antenna transmission will be described.

Digitally tunable microwave-photonic notch filters are demonstrated which are based on a differential group delay (DCD) module producing a relative delay between two orthogonal polarizations. A maximum rejection level greater than 60 dB has been stably obtained.

Traveling-wave electroabsorption modulator using intra-step-barrier quantum well and peripheral coupled waveguide are designed and tested for analog fiber link applications. The resulting device has demonstrated high optical power handling and low V/sub /spl pi// properties.

In this paper, we analyze the electroabsorption modulator in the detector/mixer and the modulator/mixer modes. Analog fiber-optic links have been studied for the transmission of signals at radio/microwave frequencies. A novel efficient frequency agile RF-converted link using EAMs as optoelectronic mixers at both transmitter and receiver. This proposed frequency converted RF link has the benefit of the optical single-side-band transmission that renders it very useful for long distance RF/microwave transmission at high center frequency and with little dispersion penalty.

A novel compact, tunable all-pass filter based on lithium niobate (LN) planar waveguide loop is proposed and demonstrated with preliminary transmission measurement. The tunability and chromatic dispersion characteristics of the device are theoretically estimated.

We perform microwave spectrum analysis by dispersing ultrashort pulses to several nanoseconds in duration. Modulating with an arbitrary microwave signal and correlating with a reference provides an output trace containing a discrete version of the microwave spectrum.

In this paper the generation of MM and sub-wave signals by heterodyning two optical signals in a photo detector is considered. Previous work in this field has shown that this approach is feasible. However, the work demonstrated so far exhibits very low power efficiency (

Transparent analog fiber link is the key element to many radio-over-fiber applications such as antenna remoting and CATV. In this paper, we present the performance of analog fiber link using advanced design of electroabsorption modulator that incorporates peripheral coupled waveguide (PCW) and intra-step-barrier quantum well (IQW) designs. High efficiency PCW-IQW electroabsorption modulator with high optical power handling property will be presented. The resultant transparent analog fiber link can be used for achieving high spurious free dynamic range.

The Generation of microwave signals by heterodyning two optical signals has been demonstrated in the past. However, so far this approach is limited in bandwidth, power and efficiency. In this paper we present an analysis of optical heterodyning in the uni-traveling carrier traveling wave photo detector taking into account the effect of ballistic electrons. The analysis is validated by comparison to measurement of an existing device made at the University of California, San Diego. Based on the above analysis a new photodiode design is made, which is expected to have a bandwidth well into the sub-MM wave region. The device exploiting the ballistic electrons effect can reach a bandwidth 2-3 times larger compared to device using velocity-saturated electrons.

A numerical modeling approach based on the microwave transmission (ABCD) matrix theory is developed for analyzing the frequency response of segmented traveling-wave electroabsorption modulators (STEAM). It is found that for 300 /spl mu/m long exemplary modulation length, the STEAM can provide much wider bandwidth (73 GHz) than the lumped-element (26 GHz) and the continuous traveling-wave (47 GHz) counter-parts, with a small penalty of E/O conversion gain if low-loss passive optical waveguide is available.

Recent advances in component technology for microwave photonics networks are discussed. Different transmitter technologies are compared in term of analog link performance. The development of high power and wide bandwidth photodiodes for analog fiber-optic link is discussed.

High power electroabsorption modulator using intra-step-barrier quantum well and peripheral coupled waveguide are designed and tested for analog fiber link applications. The resulting device has demonstrated high optical power handling and low V/sup /spl pi// properties.

This paper presents a comparison of three different types of CPW fed slot antennas integrated with a photodetector. The antennas are driven by optical power converted into microwave power using the photodetector which is directly attached to the antennas without the use of any amplifying devices. The operating frequency of these antennas is around 18.5 GHz. This paper presents the approach for matching a photodetector to a single element or to an array of elements. Measured data and simulations for various antenna/photodetector configurations are compared and discussed.

The paper presents a set of issues and solutions for the integration of a WGPD (wave guide photo detector) and a CPW (coplanar waveguide) fed three element slot antenna. Novel designs for band pass filters and low loss transmission lines are also described. The operating frequency of the antenna is around 18.5 GHz and is connected directly with the photodetector without the use of amplifier or any active elements. Measured data and simulations for various antenna/photodetector configurations are compared and discussed.

Summary form only given. Significant progress has been achieved towards the demonstration of direct wafer bonded photodetectors. This device design approach offers the freedom to combine dissimilar materials in order to fabricate novel device structures not obtainable using standard techniques. Significant device performance advantages have been demonstrated in specific device applications using wafer bonding. The results summarized here demonstrate additional progress towards defining wafer bonding as a mature technology - a manufacturable and cost-effective process applied to APDs that portends commercial application.

We review the design and fabrication of the traveling wave (TW) electrode for the EAM for high speed and high power operation. In one approach, EAMs with improved saturation properties have been demonstrated via the lowering of the hole barrier by applying appropriate strain at the well/barrier interface. An alternate approach to enhance the saturation power of the quantum well modulator is via the use of a barrier step inside the well to suppress the onset of the red shift in the quantum-confined Stark effect to a higher electric field. In these approaches, however, the saturation power is optimized without incorporating the modulation frequency considerations.