Ines Latka - Academia.edu (original) (raw)

Papers by Ines Latka

Proceedings of SPIE, Mar 19, 2013

ABSTRACT In the last years a variety of fiber optic Raman probes emerged, which are only partly s... more ABSTRACT In the last years a variety of fiber optic Raman probes emerged, which are only partly suited for in vivo applications. The in vivo capability is often limited by the bulkiness of the probes. The size is associated with the required filtering of the probes, which is necessary due to Raman scattering inside the fibers. We employed in-line fiber Bragg gratings (FBG) as notch filter for the collection path and integrated them in a novel type of Raman probe. Multicore singlemode fibers (MCSMF) were designed and drawn integrating 19 singlemode cores to achieve better collection efficiency. A Raman probe was assembled with one excitation fiber and six MCSMF with inscribed FBGs as collection fibers. The probe was characterized regarding Raman background suppression, collection efficiency, and distance dependence. First Raman measurements on brain tissue are presented.

Biomedical spectroscopy and imaging, 2012

Raman spectroscopy is an emerging biophotonic tool that advanced in recent years due to steady im... more Raman spectroscopy is an emerging biophotonic tool that advanced in recent years due to steady improvements in instrumentation for excitation and collection, and the availability of fiber optic probes. This review describes the principles of fiber optic Raman probes and their applications in cancer research of lung, breast, skin, bladder, brain, cervix, oral cavity and gastrointestinal tract.

Laser Physics Letters, 2011

All-optical microspectroscopic and tomographic tools reveal great potential for clinical dermatol... more All-optical microspectroscopic and tomographic tools reveal great potential for clinical dermatologic diagnostics, i.e., investigation of human skin and skin diseases. While optical-coherence tomography has been complemented by two-photon fluorescence tomography and second-harmonic generation tomography, a joint study of various nonlinear optical microspectroscopies, i.e., application of the recently developed multimodal imaging approach, to sizable human-tissue samples has not been evaluated up to now. Here, we present such multimodal approach combining different nonlinear optical contrast mechanisms for imaging, namely two-photon excited fluorescence (TPF), second-harmonic generation (SHG), and coherent anti-Stokes Raman scattering (CARS) into a joint microscopic experiment. We show the potential of imaging large skin areas and discuss the information obtained in a case study comparing normal skin and keloid tissue.

Journal of Biomedical Optics, Jun 28, 2018

Light: Science & Applications

The steady progress in medical diagnosis and treatment of diseases largely hinges on the steady d... more The steady progress in medical diagnosis and treatment of diseases largely hinges on the steady development and improvement of modern imaging modalities. Raman spectroscopy has attracted increasing attention for clinical applications as it is label-free, non-invasive, and delivers molecular fingerprinting information of a sample. In combination with fiber optic probes, it also allows easy access to different body parts of a patient. However, image acquisition with fiber optic probes is currently not possible. Here, we introduce a fiber optic probe-based Raman imaging system for the real-time molecular virtual reality data visualization of chemical boundaries on a computer screen and the physical world. The approach is developed around a computer vision-based positional tracking system in conjunction with photometric stereo and augmented and mixed chemical reality, enabling molecular imaging and direct visualization of molecular boundaries of three-dimensional surfaces. The proposed ...

Journal of Lightwave Technology, 2015

24th International Conference on Optical Fibre Sensors, 2015

Fiber Bragg gratings as key components in telecommunication, fiber lasers, and sensing systems us... more Fiber Bragg gratings as key components in telecommunication, fiber lasers, and sensing systems usually rely on the Bragg condition for single mode fibers. In special applications, such as in biophotonics and astrophysics, high light coupling efficiency is of great importance and therefore, multimode fibers are often preferred. The wavelength filtering effect of Bragg gratings in multimode fibers, however is spectrally blurred over a wide modal spectrum of the fiber. With a well-designed all solid multicore microstructured fiber a good light guiding efficiency in combination with narrow spectral filtering effect by Bragg gratings becomes possible.

SPIE Proceedings, 2004

As a part of the surveillance system for liquid hydrogen tanks which is developed for future spac... more As a part of the surveillance system for liquid hydrogen tanks which is developed for future space programs of the Euro-pean Space Agency, we have investigated hydrogen sensors, temperature sensors, and strain sensors, all of them based on fiber optic Bragg gratings. We present a new type of hydrogen sensor in the form of a micro-bending beam consisting of a

Measurement Science and Technology

Close meshed instrumentation or sensor networks applying conventional sensors for temperature and... more Close meshed instrumentation or sensor networks applying conventional sensors for temperature and strain monitoring may result in excessive penalties in terms of weight constraints, reliability and sensitivity to environmental conditions, and complex interfaces. The fibre-optic sensor network described in this paper is a multiplexed system of fibre Bragg grating (FBG) strain and temperature sensors and was designed and developed for a demanding space environment, but it can also be emphasized as a promising sensor technology with high potential for non-space applications. The FBG sensor network measures both strain and temperature at the measuring conditions of the structural core of the X-38 spacecraft, by means of wavelength shifts due to tensile stress on a Bragg grating. Dependent on the fixation of the fibre, either isolated from or mechanically coupled to the structure, local thermal or mechanical loads can be determined in the temperature range from -40 to +190 °C, and in the...

Journal of Biophotonics, 2011

All-optical microspectroscopic and tomographic tools have a great potential for the clinical inve... more All-optical microspectroscopic and tomographic tools have a great potential for the clinical investigation of human skin and skin diseases. However, automated optical tomography or even microscopy generate immense data sets. Therefore, in order to implement such diagnostic tools into the medical practice in both hospitals and private practice, there is a need for automated data handling and image analysis ideally implementing automized scores to judge the physiological state of a tissue section. In this contribution, the potential of an image processing algorithm for the automated classification of skin into normal or keloid based on second-harmonic generation (SHG) microscopic images is demonstrated. Such SHG data is routinely recorded within a multimodal imaging approach. The classification of the tissue implemented in the algorithm employs the geometrical features of collagen patterns that differ depending on the constitution, i.e., physiological status of the skin.

Optical Sensors 2011; and Photonic Crystal Fibers V, 2011

Microstructured optical fibers (MOFs) represent a promising platform technology for new biosensin... more Microstructured optical fibers (MOFs) represent a promising platform technology for new biosensing devices. Using MOFs with adapted cavity diameters of about 20 to 30 mum, they can be used to carry the biofluids of analytical interest. Such cavities with their walls coated by transducer material form in combination with adequate microfluidic chips a platform for fully integrated next generation plasmonic

IEEE Sensors Journal, 2012

For fully integrated next-generation plasmonic de- vices,microstructuredopticalfibers(MOFs)repres... more For fully integrated next-generation plasmonic de- vices,microstructuredopticalfibers(MOFs)representapromising platform technology. This paper describes the use of a dynamic technique to demonstrate the wet chemical deposition of gold and silver nanoparticles (NPs) within MOFs. The plasmonic struc- tures were realized on the internal capillary walls of a three-hole suspended core fiber. Electron micrographs, taken of the inside of the fiber holes, confirm the even distribution of the NP in the MOF over a length of up to 6 m. Accordingly, this procedure is highly productive and makes the resulting MOF-based sensors potentially (very) cost efficient. In proof-of-principle experiments with liquids of different refractive indices, the dependence of the localized surface plasmon resonance (LSPR) on the surroundings was confirmed. Comparing Raman spectra of MOFs with and without NP layers, each one filled with crystal violet, a significant signal enhancement demonstrates the usability of such function- alized MOFs for surface-enhanced Raman spectroscopy (SERS) experiments. NPs are circular or noncircular NPs are arranged in a nonregular order), in contrast to surface plasmon resonance (2). The sensi- tivity of the plasmon excitation to changes in the refractive index (RI) of the surrounding dielectric renders the photonic-plas- monic devices excellent candidates for optical sensing. All-fiber devices offer a number of advantages over conventional planar plasmonic structures in that they are cheap, compact, robust, flexible, and compatible with existing fiber infrastructures. In this paper, we present the experimental realization of NP-based plasmonic structures on the internal capillary walls of MOFs. It has been proposed that the evanescent field could be used for the sensing of gases and liquids within the holes of the fiber (3). The deposition of NP inside the fiber voids has the potential to explore new directions in micro/nanomaterials

IEEE Photonics Technology Letters, 2009

Endoscopic Microscopy XVII, 2022

Optica

We present a compact multimodal fiber probe that enables the simultaneous recording of nonlinear ... more We present a compact multimodal fiber probe that enables the simultaneous recording of nonlinear imaging modalities like coherent anti-Stokes Raman scattering (CARS), second harmonic generation (SHG), and two-photon excited auto-fluorescence (TPEF) for biomedical applications. The probe is based on a gradient index lens design and a multi-core fiber supplying the excitation laser light. The multi-core fiber preserves the spatial relationship between the entrance and output; therefore, the laser scanning procedure can be shifted from the distal to the proximal end of the probe. No moving parts or electric power are required in situ. The generated sample signals can be collected in the backward (epi) direction and transferred to a detection setup with a multimode fiber integrated in the probe head. The first CARS/SHG/TPEF multimodal tissue images recorded with the introduced fiber probe will be presented.

Proceedings of Spie the International Society For Optical Engineering, 2000

Operational costs during launch preparation, mission and maintenance of spacecraft do not only re... more Operational costs during launch preparation, mission and maintenance of spacecraft do not only rely on technical and logistical improvements of subsystems or components but to an even greater extent on the implementation of a Health Monitoring System.

Journal of Lightwave Technology, 2016

Fiber Bragg gratings (FBGs) in single-mode fibers, used as narrowband filters, have reached a hig... more Fiber Bragg gratings (FBGs) in single-mode fibers, used as narrowband filters, have reached a high maturity level, especially for applications in telecommunications and sensing. In spectroscopic applications, e.g., in Raman spectroscopy, FBG filters can be used to separate laser probing light from generated sensor light which simplifies Raman probes. For this purpose, light from a sample has to be collected with high efficiency into a fiber. The light collection efficiency in single-mode fibers is, however, strongly limited due to the small fiber core area. Therefore, we have investigated the possibility to use single-mode multicore fibers to increase the light collection efficiency while maintaining Bragg filter performance. An optical density filtering effect of 1.5, which is equivalent to a transmission of -15 dB, has been achieved with a FBG in a 61-core fiber. Simulations have been performed in order to clarify the influence of the fiber geometry and refractive index distribution on grating performance. The application of chirped gratings in the multicore fibers improves filter performance in comparison to homogeneous gratings.

Within the last years multimodal nonlinear imaging combining spectroscopic approaches like cohere... more Within the last years multimodal nonlinear imaging combining spectroscopic approaches like coherent anti-Stokes Raman scattering (CARS), two-photon excited auto-fluorescence (TPEF) and second harmonic generation (SHG) has shown its potential as a powerful label free imaging approach for spectral histopathology [1,2]. In order to extend the applicability of this multimodal microscopic approach under invivo conditions suitable optical fiber concepts for an endoscopic investigation of difficult to access body regions are required [3]. The most challenging spectroscopic modality to implement in a fiber probe is CARS. Here, we will introduce a novel CARS imaging fiber probe integrated into a compact endoscopic design with an overall diameter of 8 mm, consisting of 10,000 coherent light guiding elements, which preserve the spatial relationship between the entrance and the output of the fiber. Figure 1 shows a scanning electron microscope (a) and optical microscope (b) image of the excitat...