Axel Scherer

Axel Scherer
California Institute of Technology | CIT · Department of Electrical Engineering

Doctor of Philosophy

About

620
Publications
53,305
Reads
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37,254
Citations
Additional affiliations
July 1993 - present
California Institute of Technology
Position
  • Professor (Full)

Publications

Publications (620)
Article
Microscale optical devices enabled by wireless power harvesting and telemetry facilitate manipulation and testing of localized biological environments (e.g., neural recording and stimulation, targeted delivery to cancer cells). Design of integrated microsystems utilizing optical power harvesting and telemetry will enable complex in vivo application...
Article
Full-text available
Light-light switching typically requires strong nonlinearity where intense laser fields route and direct data flows of weak power, leading to a high power consumption that limits its practical use. Here we report an experimental demonstration of a metawaveguide that operates exactly in the opposite way in a linear regime, where an intense laser fie...
Article
Full-text available
As an important electron transportation phenomenon, Bloch oscillations have been extensively studied in condensed matter. Due to the similarity in wave properties between electrons and other quantum particles, Bloch oscillations have been observed in atom lattices, photonic lattices, and so on. One of the many distinct advantages for choosing these...
Article
We have developed wireless metabolic sensors for continuous in vivo monitoring of disease progression and treatment efficacy. Our sensors consist of intelligent RF tags that are embedded subdermally and powered from a reader. These chips are able to provide real-time quantitative information on the concentration of metabolites through a digital wir...
Conference Paper
Effective light-light interaction enables energy-efficient optical networks. By non-Hermitian on-chip engineering, we demonstrate asymmetric light control where intense laser field is manipulated by weak control with an extinction ratio up to 60 dB.
Conference Paper
As an important transportation phenomenon, Bloch oscillations have been studied extensively in Hermitian systems. Here by exploiting the concept of parity-time symmetry, we experimentally realize for the first time Bloch oscillations in a non-Hermitian silicon photonic lattice and show that such system contains intriguing physics.
Article
Ultrasmall scale implants have recently attracted focus as valuable tools for monitoring both acute and chronic diseases. Semiconductor optical technologies are the key to miniaturizing these devices to the long-sought sub-mm scale, which will enable long-term use of these devices for medical applications. This can also enable the use of multiple i...
Article
Full-text available
Fabrication of integrated electrochemical sensors is an important step towards realizing fully integrated and truly wireless platforms for many local, real-time sensing applications. Micro/nanoscale patterning of small area electrochemical sensor surfaces enhances the sensor performance to overcome the limitations resulting from their small surface...
Article
Electrochemical sensors are integral components of various integrated sensing applications. In this work, we provide details of optimizing electrochemical sensors for CMOS compatible integrated designs at sub-mm size scales. The focus is on optimization of electrode materials and geometry. We provide design details for both working electrode and re...
Patent
A surface wave assisted system having an aperture layer with a surface and an aperture, and a plurality of grooves around the aperture. The plurality of grooves is configured to generate an optical transfer function at the aperture by inducing a surface wave for interfering with transmission of light of a range of spatial frequency.
Patent
An implantable diagnostic device in accordance with the present disclosure includes a probe assembly that can be implemented in a variety of ways. A few example implementations include: a needle inside which is located a bio-sensor chip (the needle being insertable into a human being); a compact package containing the bio-sensor chip (the compact p...
Patent
Full-text available
An implantable biocompatible biosensor is described herein. The biosensor includes a chip layer including a plurality of holes fabricated vertically there through, a power source, one or more sensors on the chip layer and coupled to the power source and a hydrogel matrix including one or more angiogenesis stimulating factors in contact with the chi...
Article
Photonic crystal nanobeam cavities with high-quality factors are very sensitive to the dielectric properties of their surroundings. Combining this high sensitivity with a specially designed heater, we experimentally demonstrate a very sensitive optical sensor, capable of simultaneously providing heat and interrogating the refractive index of its su...
Patent
Methods for fabricating of high aspect ratio probes and deforming micropillars and nanopillars are described. Use of polymers in deforming nanopillars and micropillars is also described.
Patent
Described herein are methods for quantitative target detection in a sample through use of microbeads and related devices and systems.
Article
We demonstrate a photonic crystal nanobeam cavity optical device that provides heat and interrogates the refractive index. Experimental results show sensitivity of 97nm/RIU, temperature variation of ~100°C, and temperature switching time of a few μs.
Patent
Full-text available
Methods to fabricate reaction cartridges for biological sample preparation and analysis are disclosed. A cartridge may have a reaction chamber and openings to allow fluids to enter the chamber. The cartridge may also have handles to facilitate its use. Such cartridges may be used for polymerase chain reaction.
Article
Introduction: For developing countries, sexually transmitted infections (STIs) and their complications are ranked in the top 5 disease categories for which adults seek medical treatment. Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Trichomonas vaginalis (TV) are the three most common STIs worldwide, with TV accounting for over half...
Patent
Full-text available
Methods for fabrication of nanopillar field effect transistors are described. These transistors can have high height-to-width aspect ratios and be CMOS compatible. Silicon nitride may be used as a masking material. These transistors have a variety of applications, for example they can be used for molecular sensing if the nanopillar has a functional...
Patent
Full-text available
Structures and methods are described for optical detection of physical, chemical and/or biological samples. An optical detection structure may include a LED source, multiple filters and single or multiple sample areas. A detector may be used to record a fluorescence signal. The sample area may allow the introduction of removable cartridges.
Patent
Full-text available
Methods for fabricating self-aligned heterostructures and semiconductor arrangements using silicon nanowires are described.
Article
We have demonstrated a proof-of-concept for an athermal silicon slot waveguide using Ormocomp as a top cladding. Preliminarily theoretical and experimental results show that the slot waveguide geometry can completely cancel out its thermo-optical coefficient, by tailoring the optical mode overlap with silicon, silicon dioxide, and Ormocomp.
Article
Introduction: The CDC estimates that there are currently over 1million people living with human immunodeficiency virus (HIV-1) in the United States, with new cases increasing by approximately 50,000 each year. HIV-1 consists of four distinct groups: the major M group, and the rare N, O, and P groups, each comprising of various subtypes. Without pr...
Conference Paper
By applying chemical functionalization to a nanobeam photonic crystal cavity, an ultrasensitive gas-phase chemical sensor was demonstrated. Its nonlinear thermo-optical bi-stability is utilized to realize a novel threshold detector for cumulative chemical exposure.
Conference Paper
We present a fully implantable subcutaneous continuous glucose monitoring (CGM) microsystem on CMOS platform. The proposed design incorporates electrochemical sensing technique using an ultra-low-power potentiostatic system. It is wirelessly powered through an inductive coupling link at 900MHz and supports bidirectional data communication with an e...
Article
We have experimentally demonstrated a reconfigurable silicon thermo-optical device able to tailor its intrinsic spectral optical response by means of the thermo-optical control of individual and uncoupled resonant modes of micro-ring resonators. Preliminarily results show that the device's optical response can be tailored to build up distinct and r...
Article
Full-text available
Objectives: Infectious diseases that are largely treatable continue to pose a tremendous burden on the developing world despite the availability of highly potent drugs. The high mortality and morbidity rates of these diseases are largely due to a lack of affordable diagnostics that are accessible to resource-limited areas and that can deliver high...
Article
This letter features a new, scalable fabrication method and experimental characterization of glass-filled apertures exhibiting extraordinary transmission. These apertures are fabricated with sizes, aspect ratios, shapes and side-wall profiles previously impossible to create. The fabrication method presented utilizes top-down lithography to etch sil...
Article
Uniquely and arbitrarily shaped photonic crystal laser cavities were designed, fabricated and characterised. Room temperature lasing emitting at about 1550 nm was observed for all devices when photopumped by an 830 nm wavelength pulse laser with a pulse width of 100 ns. Continuous-wave lasing was even observed for select devices.
Article
Photonic crystal nanobeam cavities with high quality factors are very sensitive to the changes of the dielectric properties of their surroundings. Utilizing this high sensitivity and by applying chemical functionalization, an ultrasensitive chemical sensor for gases based on a nanobeam cavity was demonstrated. Limit of detection of 1.5 parts-per-bi...
Article
We report on a hybrid InP/Si photonic crystal nanobeam laser emitting at 1578 nm with a low threshold power of ∼14.7 μW. Laser gain is provided from a single InAsP quantum well embedded in a 155 nm InP layer bonded on a standard silicon-on-insulator wafer. This miniaturized nanolaser, with an extremely small modal volume of 0.375(λ/n)^3, is a promi...
Patent
Full-text available
A printed circuit board structure is coated with an encapsulant within which microfluidic channels have been formed. The microfluidic channels are formed by soldering fluidic connections to metal traces on a surface of the printed circuit board structure prior to encapsulation. The metal traces are removed by etching after encapsulation to form mic...
Conference Paper
An estimated 448 million new cases of curable sexually transmitted infections (STIs) occur every year. Some of these STIs exist without symptoms and, if untreated, can have devastating consequences on reproduction, maternal and newborn health, as well as increase the likelihood of acquisition and transmission of HIV. Traditional methods for diagnos...
Patent
Full-text available
A method for forming nanometer-sized patterns and pores in a membrane is described. The method comprises incorporating a reactive material onto the membrane, the reactive material being a material capable of lowering an amount of energy required for forming a pore and/or pattern by irradiating the membrane material with an electron beam, thus leadi...
Patent
Full-text available
A method to determine minimum etch mask dosage or thickness as a function of etch depth or maximum etch depth as a function of etch mask implantation dosage or thickness, for fabricating structures in or on a substrate through etch masking via addition or removal of a masking material and subsequent etching.
Patent
Full-text available
A method for designing, fabricating, and predicting a desired structure in and/or on a host material through defining etch masks and etching the host material is provided. The desired structure can be micro- or nanoscale structures, such as suspended nanowires and corresponding supporting pillars, and can be defined one layer at a time. Arbitrary d...
Patent
Full-text available
Methods and devices for sequencing nucleic acids are disclosed herein. Devices are also provided herein for measuring DNA with nano-pores sized to allow DNA to pass through the nano-pore. The capacitance can be measured for the DNA molecule passing through the nano-pore. The capacitance measurements can be correlated to determine the sequence of ba...
Conference Paper
Ultra small scale implants have gained lots of importance for both acute and chronic applications. Optical techniques hold the key to miniaturizing these devices to long sought sub-mm scale. This will lead towards long term use of these devices for medically relevant applications. It can also allow using multiple of these devices at the same time a...
Patent
Full-text available
A method for adhering two layers of materials is described. An additional layer of material deposited on one of the layers is used. The additional layer of material is perforated and undercut by etching away one of the layers thereby generating anchor shaped holes. The other layer is then deposited on the additional layer filling the anchor shaped...
Article
We demonstrate a successful selective growth of Si0.3Ge0.7 quantum dots (QDs) over array of p+-Si nanopillars using a low-pressure chemical vapor deposition technique, and hereafter realized high-performance QD broadband photodiodes for visible to near-infrared photodetection based on heterostructures of indium tin oxide/Si0.3Ge0.7 QD/Si pillar. Th...
Patent
Full-text available
A microfluidic fluid separator for separating target components of a fluid by filtration is described. Methods for separating target components of a fluid by filtration and methods for processing blood on a large scale with the microfluidic fluid separator are provided.
Article
We present a novel method for the encoding and decoding of multiplexed biochemical assays. The method enables a theoretically unlimited number of independent targets to be detected and uniquely identified in any combination in the same sample. For example, the method offers easy access to 48-plex PCR assays, as contrasted to the current 4-plex assa...
Patent
Full-text available
The present invention provides microfluidic devices and methods for using the same. In particular, microfluidic devices of the present invention are useful in conducting a variety of assays and high throughput screening. Microfluidic devices of the present invention include elastomeric components and comprise a main flow channel; a plurality of bra...
Article
We propose a method of forming quantum-size emitters within a pre-defined photonic crystal in a self-aligned fashion through controlled removal of quantum well layers via selective wet-chemical etching. To demonstrate the effectiveness of our method, we take the example of a two-dimensional photonic crystal slab containing multiple quantum wells at...
Article
Vertically oriented, bandgap engineered silicon double tunnel junction nanopillars were fabricated and electrically addressed. The devices were tested at liquid nitrogen and room temperatures. Distinctive staircase steps in current were observed at cryogenic temperatures indicative of the Coulomb blockade effect present in asymmetric double tunnel...
Patent
Full-text available
Methods for fabrication of microfluidic systems on printed circuit boards (PCB) are described. The PCB contains layers of insulating material and a layer or layers of metal buried within layers of insulating material. The metal layers are etched away, leaving fully enclosed microfluidic channels buried within the layers of insulating material.
Patent
Full-text available
A differential interference contrast (DIC) determination device and method utilizes an illumination source, a layer having a pair of two apertures that receive illumination from the illumination source, and a photodetector to receive Young's interference from the illumination passing through the pair of two apertures. In addition, a surface wave as...
Article
Full-text available
Neuroscience is at a crossroads. Great effort is being invested into deciphering specific neural interactions and circuits. At the same time, there exist few general theories or principles that explain brain function. We attribute this disparity, in part, to limitations in current methodologies. Traditional neurophysiological approaches record the...
Patent
Full-text available
Optical devices and methods for measuring samples while minimizing stray light are described. Such methods and devices are applicable to multiple fluid chambers with multiple sources as an integrated optical element. Light sources can be embedded onto a chip or microarray with multiple chambers, or can be part of an instrument arrangement.
Article
Full-text available
A proof-of-concept for a new and entirely CMOS compatible tunable nanobeam cavity is demonstrated in this paper. Preliminary results show that a compact nanobeam cavity (~20 μm<sup>2</sup>) with high Q-factor (~50,000) and integrated with a micro-heater atop, is able of tuning the resonant wavelength up to 15 nm with low power consumption (0.35nm/m...
Patent
Methods and arrangements to lyse a biological sample are described. The arrangements comprise a lysis tube containing the sample, one or more electromagnets generating a magnetic field, and one or more permanent magnets inside the lysis tube. The permanent magnets move and lyse the sample when a magnetic field is generated by the electromagnets.
Article
Full-text available
The use of an optically thick slab may provide versatile solutions for the realization of a current injection type laser using photonic crystals. Here, we show that a transversely higher-order defect mode can be designed to be confined by a photonic band gap in such a thick slab. Using simulations, we show that a high-Q of 10^5 is possible from a f...
Conference Paper
Full-text available
This paper will review the top down technique of ICP etching for the formation of nanometer scale structures. The increased difficulties of nanoscale etching will be described. However it will be shown and discussed that inductively coupled plasma (ICP) technology is well able to cope with the higher end of the nanoscale: features from 100nm down t...
Article
Full-text available
In order to expand the use of nanoscaled silicon structures we present a new etching method that allows us to shape silicon with sub-10 nm precision. This top-down, CMOS compatible etching scheme allows us to fabricate silicon devices with quantum behavior without relying on difficult lateral lithography. We utilize this novel etching process to cr...
Article
Electrochemical sensors are important candidates for autonomous integrated sensing applications. Such sensors can provide accurate and long-term measurements of multiple analyte for applications in complex environments e.g. in body fluids. As such sensors are made smaller and need to be fully integrated, special approaches need to be taken in order...
Article
Designing small scale integrated systems for sensing and actuation has gained lots of interest in recent years. Currently, subsystems are fabricated separately and then bonded together to form an integrated platform. This poses a fundamental limit on the size and design of such systems and also on their longevity and performance. Here, we present m...
Article
Full-text available
We show that, taking a two-dimensional photonic-crystal slab system as an example, surprisingly high quality factors (Q) over 10^5 are achievable, even in the absence of a rigorous photonic-band-gap. We find that the density of in-plane Bloch modes can be controlled by creating additional photon feedback from a finite-size photonic-crystal boundary...
Article
Full-text available
Invisibility by metamaterials is of great interest, where optical properties are manipulated in the real permittivity-permeability plane. However, the most effective approach to achieving invisibility in various military applications is to absorb the electromagnetic waves emitted from radar to minimize the corresponding reflection and scattering, s...
Chapter
Fabrication of precision micro- and nanoscale structures in silicon demands exacting control over pattern transfer during etching. The most utilized method to enable this pattern transfer anisotropically is plasma etching with an inductively couple plasma reactive ion etcher. When properly used, these machines can etch high-aspect-ratio structures...
Conference Paper
We show that the properties of silicon can be changed profoundly when nanofabricated to below 5nm, resulting in larger bandgap emission and more efficient light generation. Moreover, three-dimensional nanostructures can be fabricated at these nanoscale dimensions by dynamic control over the dry etching process.
Article
An error was made in the calculation of the photonic crystal mode volume. Fixing this error increases our mode volume by a factor of 2 and makes our claim of highest Q/V invalid.
Chapter
The design, fabrication, and characterization of passive one-dimensional photonic crystal nanobeam cavities is presented. Silicon is chosen as the material system due to its ability to provide very high quality factors, a necessary prerequisite for solid state cavity quantum electrodynamics experiments, and its applicability to large scale hybrid d...
Article
Full-text available
A proof-of-concept for a new and entirely CMOS compatible thermo-optic reconfigurable switch based on a coupled ring resonator structure is experimentally demonstrated in this paper. Preliminary results show that a single optical device is capable of combining several functionalities, such as tunable filtering, non-blocking switching and reconfigur...
Article
There is an increasing need for affordable, thermostable PCR reagents that can be used for diagnostic testing in resource limited settings. The development of point-of-care devices in such settings is highly dependent on the availability and efficacy of thermostable reagents. Here, we assess the thermostability of commercial, intercalating dye-base...
Article
The 1989 VCSEL-advance by this group, which marked a turning point in VCSEL development efforts, was a curious culmination built upon outside publications, optical innovations from the group, risky-research funding, and resolute inter-company collaboration. Article not available.
Conference Paper
We demonstrate room temperature continuous wave lasing in bottom-up photonic crystal cavities formed by patterned III-V nanopillars. Single-cell high-Q photonic crystal cavities are formed with nanopillars by selective-area epitaxy. Control of the nanopillar geometry and heterostructures allows for high-Q and large confinement factor, resulting in...
Article
When combined with high index constrast slabs in which light can be efficiently guided, microfabricated two-dimensional photonic bandgap mirrors provide us with the geometries needed to confine light into extremely small volumes. We show that these high Q cavities now make it possible to define microcavity lasers which function at room temperature...
Article
Full-text available
An error was made in the calculation of the photonic crystal mode volume. Fixing this error increases our mode volumes by a factor of two and makes our claim of highest Q/V invalid.
Article
Full-text available
A photonic crystal (PhC) nanocavity formed in an optically very thick slab can support reasonably high-Q modes for lasing. Experimentally, we demonstrate room-temperature pulsed lasing operation from the PhC dipole mode emitting at 1324 nm, which is fabricated in an InGaAsP slab with thickness (T) of 606 nm. Numerical simulation reveals that when T...
Article
Full-text available
In this work we study the effect of thin-film deposition on the quality factor (Q) of silicon nanobeam cavities. We observe an average increase in the Q of 38±31% in one sample and investigate the dependence of this increase on the initial nanobeam hole sizes. We note that this process can be used to modify cavities that have larger than optimal ho...
Article
Full-text available
Fan et al. raised technical concerns about our study regarding the Lorentz reciprocity theorem, with which we completely agree. Unfortunately, we incorrectly used the term “nonreciprocal” to describe the behavior of electromagnetic propagation in our devices. In our paper, this term does not refer to Lorentz reciprocity but to the asymmetric mode c...
Article
We have developed new low threshold surface emitting laser designs with dielectric high reflectivity top mirrors. Here, we describe the characteristics of these surface emitting vertical cavity lasers (VCSELs) which exhibit stable mode patterns and low threshold currents. The new device fabrication sequence which we employ is able to adjust the emi...
Article
The directed growth of III-V nanopillars is used to demonstrate bottom-up photonic crystal lasers. Simultaneous formation of both the photonic band gap and active gain region is achieved via catalyst-free selective-area metal-organic chemical vapor deposition on masked GaAs substrates. The nanopillars implement a GaAs/InGaAs/GaAs axial double heter...