Avantes

Articles

This application note explores the fundamentals of fluorescence and different types of measurement setups. 

Fluorescence Spectroscopy: Theory and System Design

This application note demonstrates the performance of the company instrument for the analysis of semi volatiles based upon the specifications of USEPA method 8270D. This application note describes the importance of spectroscopy for the future of smart agriculture.


Spectroscopy and the Future of Agriculture

	The spectral information around us can be used in an expanding realm of technologies, especially as the detecting devices get smaller. To learn more about this, Spectroscopy magazine talked with Ger Loop, who is the Product Manager of Avantes, to discuss the future of miniature spectroscopy and the role Avantes wants to play in it.

Check out the associated whitepaper here!

Podcasts

The spectral information around us can be used in an expanding realm of technologies, especially as the detecting devices get smaller. To learn more about this, Spectroscopy magazine talked with Ger Loop, who is the Product Manager of Avantes, to discuss the future of miniature spectroscopy and the role Avantes wants to play in it.

The Future of Miniature Spectroscopy

Even though no current electronics is fast enough to measure femtosecond lasers, an estimation of the pulse duration, peak wavelength, and relative intensity is possible.

The femtosecond time scale is out of reach for even the fastest electronics, so to perform pulse diagnostics other measurement techniques need to be used.  

The AvaSoft-Femto add-on turns your Avantes spectrometer into a femtosecond laser diagnostic tool that can provide you with an estimation of the transform limited pulse duration as well as measuring the peak wavelength and relative intensity of the laser output. Using the add-on users can also easily export the measurements to spread sheet programs like Microsoft Excel for record keeping or further analysis. 

Many femtosecond mode-locked lasers can generate nearly bandwidth-limited pulses, especially when they are based on soliton mode locking. A femtosecond mode-locked Ti:Sapphire laser when fully optimized propagates a soliton-like pulse with a hyperbolic secant squared function intensity distribution in the frequency domain. 

Figure 1: An AvaSpec-2048L is used for femtosecond laser measurements.			

By accurately measuring the spectral output of a femtosecond mode-locked Ti:Sapphire and using the time-bandwidth product of different pulse shapes (Gaussian, Hyperbolic Secant Squared, Lorentzian) the lower limit for the pulse duration can be determined. 

The full-width at half maximum (FWHM) is accurately measured using an Avantes spectrometer and this is then used in combination with a value of K (that is dependent on the symmetrical shape of the pulse) to calculate the transform limited pulse duration; 			

The AvaSoft-Femto software allows for a quick and convenient way to show the transform limited pulse duration according to the pulse shape selected in the software. The complete Femto package also provides a good general purpose spectrometer that can be used for various applications in the lab. 

Table I: Values for K depending on the pulse shape.			

When using AvaSoft-Femto with an Avantes spectrometer that doesn't have an order sorting filter installed, you can also use the system to measure laser lines in the ~300–600 nm range by observing them in the second order. This means 500 nm will show up as 1000 nm on the spectrometer. Lines in the ~200–300 nm range can be seen in the third order (that is, 300 nm will show up at 900 nm on the spectrometer). The spectrometer included in the Ava-Femto package can be used for second and third order measurements. 

The AvaSoft-Femto can be used with virtually any existing Avantes spectrometer provided it covers the required wavelength range. 

				Oude Apeldoornseweg 28, 7333 NS Apeldoorn, The Netherlands			

Ultrafast Laser Diagnostics

For the optimization of photodynamic therapy the spectroscopic detection of photosensitizer molecules, which are selectively enriched in tumour cells, can be useful. In patients with cancer lesions, Chlorin e6 was administered and the typical fluorescence peak was measured using blue light excitation.

The green porphyrin Chlorin e6 is known as a photosensitizer for systemic photodynamic therapy (PDT) for cancer treatment. The molecules accumulate after an intravenous administration selectively in tumor cells. With blue LED or laser light sources the molecules can be excited to a red fluorescence. In order to this, tumor cells and the dimension of tumors can be monitored. Under red light excitation photochemical processes are leading to the generation of singlet oxygen, which is a highly reactive and cell toxic substance. Tumour cells can be killed very selectively and with low side effects to the patients. 

Figure 1: Maximum of the fluorescence signal in the course of time. Tumor tissue in comparison to normal skin.			

In single case studies Chlorin e6 was given to patients with morbus bowen´s disease (precancerous lesion) and basal cell carcinoma. The patients were treated with different doses from 0,5 mg/kg body weight to 1 mg/kg body weight. The fluorescence signal at 670 nm which is proportional to the amount of Chlorin e6 was measured with a fiber optic spectrometer system (AvaSpec-2048-USB2, Avantes BV, The Netherlands) and illumination with an LED light source at 400 nm (AvaLight-LED Light source, Avantes BV, The Netherlands). The light was delivered over a bifurcated reflection probe (FCR-19UV200-2ME-S2 15, Avantes) with 15 illumination fibers and 4 read fibers. 

Figure 2: Basalioma behind the ear before and half a year after treatment.			

With a dose of 0,8 mg/kg bodyweight the optimal accumulation in tumor tissue was reached 3 h after application. In basal cell carcinomas of the skin, we reached tumor to tissue ratios of 12:1.  

In morbus bowen´s lesions ratios of 7 to 1 were reached. Lower doses of 0,5 mg/kg bw led to lower enrichment and a further bolus was given to reach the 0,8 mg level (see Figure 1). At the point of maximum enrichment the therapy was performed with a 2 W red diode laser (Vision, Germany) successfully. 

The fiber-spectroscopic measurement of the amount of photosensitizer helps to optimize the PDT-treatment, in order to find the right light dose and the optimal point of time for the treatment. Chlorin e6 as a tumor selective agent showed a high tumor to tissue ratio and with the excellent acceptance with low side effects it is a highly potent photosensitizer. In future fiber optic probes, positioned over endoscopes, will be tested for measurements in inner organs like lung and bladder. 

Soerense Zand Noord 26, NL-6961 RB Eerbeek, The Netherlands 

tel. +31-(0)-313-670170; fax +49(0)1721075902  