- I used to work as an Research Fellow of the Academy of Finland at Aalto University and Centre for Metrology and Accre... moreI used to work as an Research Fellow of the Academy of Finland at Aalto University and Centre for Metrology and Accreditation, both in Espoo, Finland. In June 2013 I moved on to Neste Oil Corporation, Finland to head their Research Analytics Group.edit
For monitoring environmental pollution or detecting toxic, inflammable and explosive gases [1-2], which pose major risk on health, safety and security, photoacoustic (PA) spectroscopy is one of the applied detection methods because of its... more
For monitoring environmental pollution or detecting toxic, inflammable and explosive gases [1-2], which pose major risk on health, safety and security, photoacoustic (PA) spectroscopy is one of the applied detection methods because of its high sensitivity and selectivity [3-4]. In the gas sensing applications, the non-radiative relaxation processes of electromagnetic-radiation-induced excited molecules generate heat and consequently produce pressure waves, which give rise to the PA signal. One of the common methods for detecting the PA signal employs a capacitive microphone. However, a capacitive microphone has several limitations including the nonlinear response of the membrane in sensing the external pressure. Apart from that, for improving the sensitivity, the gap between the membrane and the backplane of the capacitive condenser cannot be reduced below a certain limit, as the gas cannot anymore flow freely through such narrow region due to viscous effect [5]. An alternative appr...
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The ultraviolet (UV) spectral region is of great importance for analytic spectroscopy because the resonance lines of most of the elements and electronic transitions of molecules lie in the UV. The absorption cross sections of electronic... more
The ultraviolet (UV) spectral region is of great importance for analytic spectroscopy because the resonance lines of most of the elements and electronic transitions of molecules lie in the UV. The absorption cross sections of electronic transitions are larger than the ones of ro-...
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Research Interests:
Research Interests:
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ABSTRACT The aim of this work was to develop a cost effective hyperspectral instrument and to demonstrate the acquisition of IR reflection spectra over long distances.
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ABSTRACT We study experimentally the application of supercontinuum (SC) sources in incoherent broadband cavity-enhanced absorption spectroscopy (IBB-CEAS). By carefully tailoring the SC spectrum to match the high reflectivity bandwidth of... more
ABSTRACT We study experimentally the application of supercontinuum (SC) sources in incoherent broadband cavity-enhanced absorption spectroscopy (IBB-CEAS). By carefully tailoring the SC spectrum to match the high reflectivity bandwidth of the mirrors, an unprecedented spectral brightness can be achieved at wavelengths where the effective absorption path length exceeds 40 km, making the fiber-based SC an ideal match for the simple and robust IBB-CEAS technique. We demonstrate the potential of SC sources in broadband measurement of weak overtone transitions of carbon dioxide and methane and compare its performances with that of typical superluminescent diode (SLD) source.
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ABSTRACT The aim of this work was to develop a cost effective hyperspectral instrument and to demonstrate the acquisition of IR reflection spectra over long distances.
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ABSTRACT We study experimentally the application of supercontinuum (SC) sources in incoherent broadband cavity-enhanced absorption spectroscopy (IBB-CEAS). By carefully tailoring the SC spectrum to match the high reflectivity bandwidth of... more
ABSTRACT We study experimentally the application of supercontinuum (SC) sources in incoherent broadband cavity-enhanced absorption spectroscopy (IBB-CEAS). By carefully tailoring the SC spectrum to match the high reflectivity bandwidth of the mirrors, an unprecedented spectral brightness can be achieved at wavelengths where the effective absorption path length exceeds 40 km, making the fiber-based SC an ideal match for the simple and robust IBB-CEAS technique. We demonstrate the potential of SC sources in broadband measurement of weak overtone transitions of carbon dioxide and methane and compare its performances with that of typical superluminescent diode (SLD) source.
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Abstract Spectrometers employing supercontinuum sources and cavity-enhanced absorption spectroscopy will be discussed. Such spectrometers allow simultaneous measurement of multiple trace species both in the gas and liquid phase at high... more
Abstract Spectrometers employing supercontinuum sources and cavity-enhanced absorption spectroscopy will be discussed. Such spectrometers allow simultaneous measurement of multiple trace species both in the gas and liquid phase at high sensitivity and speed.
Research Interests:
Research Interests:
Wavelength tuning and spectral characteristics of commercially available standard laser diodes are far from ideal, and thus many applications in the near infrared are limited to the use of relatively expensive distributed feedback (DFB)... more
Wavelength tuning and spectral characteristics of commercially available standard laser diodes are far from ideal, and thus many applications in the near infrared are limited to the use of relatively expensive distributed feedback (DFB) laser diodes. External cavity diode lasers (ECDL), ...
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We present a spectrometer for sensitive absorption measurements in liquids across broad spectral bandwidths. The spectrometer combines the unique spectral properties of incoherent supercontinuum light sources with the advantages of cavity... more
We present a spectrometer for sensitive absorption measurements in liquids across broad spectral bandwidths. The spectrometer combines the unique spectral properties of incoherent supercontinuum light sources with the advantages of cavity ring-down spectroscopy, which is a self-calibrating technique. A custom-built avalanche photodiode array is used for detection, permitting the simultaneous measurement of ring-down times for up to 64 different spectral components at nanosecond temporal resolution. The minimum detectable absorption coefficient was measured to be 3.2 × 10(-6) cm(-1) Hz(-1/2) at 527 nm. We show that the spectrometer is capable of recording spectral differences in trace levels of blood before and after hemolysis.
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In this paper, frequency-doubled diode laser based on a transmission diffraction grating for high-resolution atomic absorption spectroscopy in the UV at 325 nm is developed. The fundamental single-mode beam is frequency-doubled with a... more
In this paper, frequency-doubled diode laser based on a transmission diffraction grating for high-resolution atomic absorption spectroscopy in the UV at 325 nm is developed. The fundamental single-mode beam is frequency-doubled with a lithium iodate crystal. And CW output power of 40 nW was obtained.
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Laurila, T., Oikari, R., Pöyhönen, T., Joutsenoja, T., Mikkola, P., Hernberg, R., Ranki-Kilpinen, T., Järvi, J. & Taskinen, P. 2003. Experimental studies on particle temperatures in flash smelting of copper. Copper 2003, 30 November - 3... more
Laurila, T., Oikari, R., Pöyhönen, T., Joutsenoja, T., Mikkola, P., Hernberg, R., Ranki-Kilpinen, T., Järvi, J. & Taskinen, P. 2003. Experimental studies on particle temperatures in flash smelting of copper. Copper 2003, 30 November - 3 December 2003, Santiago, Chile 12 p. ... This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Putkiranta, M., Manninen, A., Rostedt, A., Laurila, T., Saarela, J., Marjamäki, M., Keskinen, J. & Hernberg, R. 2006. UV laser induced fluorescence of individual bioaerosol particles. In: Biswas, P. et al. (eds.). Proceedings of the... more
Putkiranta, M., Manninen, A., Rostedt, A., Laurila, T., Saarela, J., Marjamäki, M., Keskinen, J. & Hernberg, R. 2006. UV laser induced fluorescence of individual bioaerosol particles. In: Biswas, P. et al. (eds.). Proceedings of the Seventh International Aerosol Conference, St. Paul, Minnesota, USA, September 10-15, 2006 p. 992. ... This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Lehtinen, J., Laurila, T., Reivonen, T., Levänen, E., Mäntylä, T., Lassila, L., Tuusa, S., Kienanen, P., Vallittu, P. & Hernberg, R. 2005. Development of optically functional fiber-reinforced composite for medicine and dentistry. In:... more
Lehtinen, J., Laurila, T., Reivonen, T., Levänen, E., Mäntylä, T., Lassila, L., Tuusa, S., Kienanen, P., Vallittu, P. & Hernberg, R. 2005. Development of optically functional fiber-reinforced composite for medicine and dentistry. In: Lundström, R. et al. (eds.). 13th Nordic Baltic Conference of Biomedical Engineering and Medical Physics, 13NBC 2005, June 13th-17th, 2005, Umeå, Sweden Ruotsi. 9, pp. 180-181. ... This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
AB3: Työn tarkoituksena oli paineistettuun pölypölttoon soveltuvan kuituoptisen kaksiväripyrometrin suunnittelu ja rakentaminen. Kaksiväripyrometri suunniteltiin ja optimoitiin Aachenin teknillisen korkeakoulun rakenteilla olevaan, hiiltä... more
AB3: Työn tarkoituksena oli paineistettuun pölypölttoon soveltuvan kuituoptisen kaksiväripyrometrin suunnittelu ja rakentaminen. Kaksiväripyrometri suunniteltiin ja optimoitiin Aachenin teknillisen korkeakoulun rakenteilla olevaan, hiiltä polttavaan 400 kW: n tutkimusreaktoriin. Valmiilla mittalaitteella tehtiin koemittauksia laboratorio-olosuhteissa Saksassa. Mittaussondin suunnittelussa on huomioitava mittaustilavuuden koko sekä mahdollinen jäähdytetyn taustan ja optiikan tarve.
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Abstract Spectrometers employing supercontinuum sources and cavity-enhanced absorption spectroscopy will be discussed. Such spectrometers allow simultaneous measurement of multiple trace species both in the gas and liquid phase at high... more
Abstract Spectrometers employing supercontinuum sources and cavity-enhanced absorption spectroscopy will be discussed. Such spectrometers allow simultaneous measurement of multiple trace species both in the gas and liquid phase at high sensitivity and speed.
We present a spectrometer for sensitive absorption measurements in liquids across broad spectral bandwidths. The spectrometer combines the unique spectral properties of incoherent supercontinuum light sources with the advantages of cavity... more
We present a spectrometer for sensitive absorption measurements in liquids across broad spectral bandwidths. The spectrometer combines the unique spectral properties of incoherent supercontinuum light sources with the advantages of cavity ring-down spectroscopy, which is a self-calibrating technique. A custom-built avalanche photodiode array is used for detection, permitting the simultaneous measurement of ring-down times for up to 64 different spectral components at nanosecond temporal resolution. The minimum detectable absorption coefficient was measured to be 3.2 × 10(-6) cm(-1) Hz(-1/2) at 527 nm. We show that the spectrometer is capable of recording spectral differences in trace levels of blood before and after hemolysis.
Research Interests:
Research Interests:
Saarela, J., Manninen, A., Putkiranta, M., Rostedt, A., Laurila, T., Marjamäki, M., Keskinen, J. & Hernberg, R. 2007. Fluorescence excitation spectroscopy of riboflavin-doped sodium chloride particles. In: Saarinen, JJ (ed.). Proceedings... more
Saarela, J., Manninen, A., Putkiranta, M., Rostedt, A., Laurila, T., Marjamäki, M., Keskinen, J. & Hernberg, R. 2007. Fluorescence excitation spectroscopy of riboflavin-doped sodium chloride particles. In: Saarinen, JJ (ed.). Proceedings of the Optics Days 2007, 3-4 May, 2007, Lappeenranta p. 62. ... This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
A hyperspectral remote sensing instrument employing a novel near-infrared supercontinuum light source has been developed for active illumination and identification of targets. The supercontinuum is generated in a standard normal... more
A hyperspectral remote sensing instrument employing a novel near-infrared supercontinuum light source has been developed for active illumination and identification of targets. The supercontinuum is generated in a standard normal dispersion multi-mode fiber and has 16 W total optical output power covering 1000 nm to 2300 nm spectral range. A commercial 256-channel infrared spectrometer was used for broadband infrared detection. The feasibility of the presented hyperspectral measurement approach was investigated both indoors and in the field. Reflection spectra from several diffusive targets were successfully measured and a measurement range of 1.5 km was demonstrated.
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Research Interests:
A tunable diode laser photoacoustic setup based on a recently demonstrated cantilever technique was used for sensitive detection of oxygen. As light sources, we used a distributed feedback (DFB) diode laser and a vertical-cavity... more
A tunable diode laser photoacoustic setup based on a recently demonstrated cantilever technique was used for sensitive detection of oxygen. As light sources, we used a distributed feedback (DFB) diode laser and a vertical-cavity surface-emitting (VCSEL) laser, both operating near 760 nm. With the 30 mW DFB laser a noise-equivalent detection limit of 20 ppm for oxygen was obtained, while a detection limit of 5 ‰ was achieved with the VCSEL having an output power of 0.5 mW. Our results yield a noise-equivalent sensitivity of 4.8×10-9 cm-1W Hz-1/2 and demonstrate the potential of this technique for compact and sensitive measurement of oxygen.
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A compact and sensitive photoacoustic setup has been developed based on a recently demonstrated cantilever technique. A micromechanical cantilever transducer is attached to a cylindrical photoacoustic cell and the cantilever’s deflection... more
A compact and sensitive photoacoustic setup has been developed based on a recently demonstrated cantilever technique. A micromechanical cantilever transducer is attached to a cylindrical photoacoustic cell and the cantilever’s deflection is monitored with a compact Michelson interferometer. A commercial 1-Watt optical fiber amplifier was used to enhance the performance of the system. A normalized sensitivity of 1.4×10-10 cm-1 W Hz-1/2 was achieved in the detection of carbon dioxide at 1572 nm wavelength. Using 34 mW optical power from a DFB diode laser, the noise-equivalent detection limit for carbon dioxide at this wavelength is 4.0 ppm. Employing the fiber amplifier, we improved the sensitivity to yield measurement of sub-ppm concentrations.
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Research Interests: Mechanical Engineering, Environmental Monitoring, Aerosols, Flow Injection Analysis, Lasers, and 11 moreApplied Optics, Optical physics, Particle Size, Cross Section, Reproducibility of Results, Microspheres, Sensitivity and Specificity, Equipment Design, Equipment Failure Analysis, Electrical And Electronic Engineering, and Air Pollutants
An efficient calibration method has been developed for broad-bandwidth cavity enhanced absorption spectroscopy. The calibration is performed using phase shift cavity ring-down spectroscopy, which is conveniently implemented through use of... more
An efficient calibration method has been developed for broad-bandwidth cavity enhanced absorption spectroscopy. The calibration is performed using phase shift cavity ring-down spectroscopy, which is conveniently implemented through use of an acousto-optic tunable filter (AOTF). The AOTF permits a narrowband portion of the SC spectrum to be scanned over the full high-reflectivity bandwidth of the cavity mirrors. After calibration the AOTF is switched off and broad-bandwidth CEAS can be performed with the same light source without any loss of alignment to the set-up. We demonstrate the merits of the method by probing transitions of oxygen molecules O2 and collisional pairs of oxygen molecules (O2)2 in the visible spectral range.
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Research Interests:
Supercontinuum radiation sources are becoming ubiquitous in a large range of scientific applications. They offer enormous spectral bandwidth and high brightness ideal attributes for applications in molecular sensing, improving both speed... more
Supercontinuum radiation sources are becoming ubiquitous in a large range of scientific applications. They offer enormous spectral bandwidth and high brightness ideal attributes for applications in molecular sensing, improving both speed and sensitivity of detection. There are challenges too, however: supercontinuum generation is an inherently noisy process and some wavelength regions of interest for molecular sensing are as of yet difficult to reach. We review the current state-of-the-art of molecular sensing with supercontinuum radiation and reflect critically on current challenges and future opportunities.
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Research Interests:
Supercontinuum radiation sources are attractive for spectroscopic applications owing to their broad wavelength coverage, which enables spectral signatures of multiple species to be detected simultaneously. Here we report the first use of... more
Supercontinuum radiation sources are attractive for spectroscopic applications owing to their broad wavelength coverage, which enables spectral signatures of multiple species to be detected simultaneously. Here we report the first use of a supercontinuum radiation source for broadband trace gas detection using a cavity enhanced absorption technique. Spectra were recorded at bandwidths of up to 100 nm, encompassing multiple absorption bands of H(2)O, O(2) and O(2)-O(2). The same instrument was also used to make quantitative measurements of NO(2) and NO(3). For NO(3) a detection limit of 3 parts-per-trillion in 2 s was achieved, which corresponds to an effective 3sigma sensitivity of 2.4 x 10(-9) cm(-1)Hz(-1/2). Our results demonstrate that a conceptually simple and robust instrument is capable of highly sensitive broadband absorption measurements.
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We present a compact and robust analyzer employing micro-plasma emission spectroscopy for real-time determination of metal concentrations in flowing water samples. The analyzer has been characterized by measuring Na, Mn and Ag at mg/L... more
We present a compact and robust analyzer employing micro-plasma emission spectroscopy for real-time determination of metal concentrations in flowing water samples. The analyzer has been characterized by measuring Na, Mn and Ag at mg/L concentrations. The intensity fluctuations of the emission signals have been significantly reduced by applying the Boltzmann plot method to account for variations in the excitation temperature and the number of emitting particles.
We present an adaptive numerical filter for analyzing fiber-length dependent properties of optical rogue waves, which are highly intense and extremely red-shifted solitons that arise during supercontinuum generation in photonic crystal... more
We present an adaptive numerical filter for analyzing fiber-length dependent properties of optical rogue waves, which are highly intense and extremely red-shifted solitons that arise during supercontinuum generation in photonic crystal fiber. We use this filter to study a data set of 1000 simulated supercontinuum pulses, produced from 5 ps pump pulses containing random noise.
A novel spectrometer for the rapid and sensitive detection of liquid phase analytes at trace concentrations is presented. Broad bandwidth supercontinuum radiation was coupled into a linear optical cavity incorporating an intracavity... more
A novel spectrometer for the rapid and sensitive detection of liquid phase analytes at trace concentrations is presented. Broad bandwidth supercontinuum radiation was coupled into a linear optical cavity incorporating an intracavity liquid-sample cuvette. Cavity enhanced absorption spectra of trace species covering more than 300 nm were acquired on time scales of milliseconds. Single shot acquisition times of 10-50 ms are demonstrated here. The effective absorption path length exceeds 2 m in sample volumes measuring 2.7 mL.
Abstract Interactions between supercontinuum (SC) light pulses, produced by the propagation of rapidly sequenced picosecond pump laser pulses along a photonic crystal fiber, result in spectral broadening, which we attribute to interpulse... more
Abstract Interactions between supercontinuum (SC) light pulses, produced by the propagation of rapidly sequenced picosecond pump laser pulses along a photonic crystal fiber, result in spectral broadening, which we attribute to interpulse soliton collisions.
The anesthetic agent propofol (2, 6-diisopropylphenol) is the most widely used intravenously administered drug in general anesthesia. However, a viable online capability to monitor metabolized levels of propofol in patients does not... more
The anesthetic agent propofol (2, 6-diisopropylphenol) is the most widely used intravenously administered drug in general anesthesia. However, a viable online capability to monitor metabolized levels of propofol in patients does not currently exist. Here we show for the first time that optical spectroscopy has good potential to detect metabolized propofol from patients' exhaled breath. We present quantitative absorption measurements of gas phase propofol both in the ultraviolet and middle-infrared spectral regions.
A white light-emitting diode (LED) with emission between 420 and 700 nm and a supercontinuum (SC) source with emission between 450 and 2500 nm have been compared for use in evanescent wave broadband cavity-enhanced absorption spectroscopy... more
A white light-emitting diode (LED) with emission between 420 and 700 nm and a supercontinuum (SC) source with emission between 450 and 2500 nm have been compared for use in evanescent wave broadband cavity-enhanced absorption spectroscopy (EW-BB-CEAS). The method is calibrated using a dye with known absorbance.
Abstract A photoacoustic (PA) sensor has been developed for the detection of nitrogen dioxide (NO 2). Ten amplitude-modulated high-power light emitting diodes (LEDs), emitting a total optical power of 9 W at 453 nm, are used to excite the... more
Abstract A photoacoustic (PA) sensor has been developed for the detection of nitrogen dioxide (NO 2). Ten amplitude-modulated high-power light emitting diodes (LEDs), emitting a total optical power of 9 W at 453 nm, are used to excite the photoacoustic signal in NO 2. The LEDs are attached to the circumference of a cylindrical PA cell. The induced longitudinal acoustics waves are detected using two electromechanical film stacks, located at the ends of the cell.
Abstract Supercontinuum radiation sources are attractive for spectroscopic applications owing to their broad wavelength coverage, which enables spectral signatures of multiple species to be detected simultaneously. Here we report the... more
Abstract Supercontinuum radiation sources are attractive for spectroscopic applications owing to their broad wavelength coverage, which enables spectral signatures of multiple species to be detected simultaneously. Here we report the first use of a supercontinuum radiation source for broadband trace gas detection using a cavity enhanced absorption technique. Spectra were recorded at bandwidths of up to 100 nm, encompassing multiple absorption bands of H 2 O, O 2 and O 2-O 2.
Abstract An efficient calibration method has been developed for broad-bandwidth cavity enhanced absorption spectroscopy. The calibration is performed using phase shift cavity ring-down spectroscopy, which is conveniently implemented... more
Abstract An efficient calibration method has been developed for broad-bandwidth cavity enhanced absorption spectroscopy. The calibration is performed using phase shift cavity ring-down spectroscopy, which is conveniently implemented through use of an acousto-optic tunable filter (AOTF). The AOTF permits a narrowband portion of the SC spectrum to be scanned over the full high-reflectivity bandwidth of the cavity mirrors.
Abstract Light extracting optical fibers are used in various applications, for example, in sensing and lighting. Combining light extracting optical fibers with light curable dental materials opens up possibilities of creating a new type... more
Abstract Light extracting optical fibers are used in various applications, for example, in sensing and lighting. Combining light extracting optical fibers with light curable dental materials opens up possibilities of creating a new type of in situ-mouldable dental implant. In the dental application the extracted light intensity must be controlled along the fiber. The efficiency of light extraction can be controlled by creating suitable light scattering objects, such as holes or grooves, on the fiber.
The ultraviolet (UV) spectral region is of great importance for analytic spectroscopy because the resonance lines of most of the elements and electronic transitions of molecules lie in the UV. The absorption cross sections of electronic... more
The ultraviolet (UV) spectral region is of great importance for analytic spectroscopy because the resonance lines of most of the elements and electronic transitions of molecules lie in the UV. The absorption cross sections of electronic transitions are larger than the ones of ro-...