Frist ,what type of laser source have been used in your experiment ?

What type of detection method have been used ?

This case couldn't be happen .

Do you try with other light ?.

Good luck

This is due to that the blood absorption spectrum is match with the emission spectrum of this laser, so the laser will totally absorbed by blood.

Have you dried an empty couvette first to see if the detector is picking up almost the full intensity? If so then start with plain water and then start using highly diluted samples of the original blood sample to see if you get any reading at all.

@srini vasan, dear yes we have followed the exact procedure. When blood is added to the chemical normasline that is used to dilute it, then we get laser beam out to photodetector. Else beam does not pass through the blood. Is it blood bonding that scatters light or absorption?

@ srini vasan. В первую очередь следует получить спектр поглощения ( непропускания ) исследуемого образца.

Анализ этого спектра должен дать подсказку, какую длину волны какого лазера использовать для исследования спектров пропускания . В О.

Tissue and blood are fairly transparent to red and infrared light (you can pass red light through your finger for example), but most likely strong scattering is preventing you from getting a signal. You could try using an integrating sphere to detect the scattered light

First of all, it is necessary to obtain the absorption spectrum (non-transmission) of the test sample.

An analysis of this spectrum should give a hint what wavelength of which laser to use for the study of transmission spectra. V.O.

If the blood is seen red, it is because the 'red' wavelengths are mainly reflected (/ scattered). Thus, the "red" wavelength of your laser is certainly not transmitted but reflected as well.

For a more scientific conclusion, check whether the emission wavelength of your laser is part or not of the absorption/reflection/transmission spectrum(s) of your blood sample.

This is possible either due to high absorption or high scattering of the laser from the sample.

In published blood absorption spectrum you see that for light wavelength more than 600 nm extinction coefficient (absorption) drops down by more than order of magnitude. This is the reason why visible blood color is red. From the other hand, red blood cell is flat disc with diameter of few micrometers, so it is several times bigger than light wavelength. Additionally, refractive index of red blood cell is rather different relative to one of blood plasma. By these reasons scattering of light by red blood cells is very efficient and such scattering is main factor of strong decreasing of transmitted red laser light. It is possible to observe it only for very thin blood cuvette thickness.