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New method for exposing mammalian cells to intense laser radiation using the evanescent fields created in optical waveguides
Author(s) -
Cox Hollace L.,
Chang William S. C.,
Brandt Karen L.,
Steward Palmer G.
Publication year - 1978
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.594517
Subject(s) - waveguide , materials science , optics , laser , optoelectronics , absorption (acoustics) , radiation , electric field , excited state , physics , atomic physics , quantum mechanics , composite material
A new method has been developed for exposing mammalian cells to intense laser radiation, using optical waveguides. Attached cells are exposed to the intense evanescent tail associated with the propagating waveguide modes. This technique allows a monolayer of attached cells covering a wide area on the waveguide surface to be exposed to optical power densities in the 10 5 –10 8 W/cm 2 range. Waveguide modes containing power densities in this range are easily excited by moderate‐power continuous‐wave (CW) lasers. A monolayer consisting of an asynchronous population of 10 5 EMT‐6 cells was plated over a 2‐cm 2 area on the top surface of an optical waveguide. This waveguide was fabricated by rf sputtering Ba−glass on a glass microscope slide used as a substrate. The area occupied by the cells was defined by a cell chamber constructed on top of the waveguide and filled with alpha‐MEM growth medium. TE 0 and TE 1 waveguide modes were excited in the waveguide using a single mode (TEM 00 and single longitudinal mode) CW Ar + ‐ion laser at a wavelength of 5145 Å. Only 33.7% of the cells survived when the maximum power density and electric field strength within the waveguide reached 4×10 5 W/cm 2 and 10 4 V/cm, respectively. No appreciable absorption of the laser radiation was detected due to the presence of the cells or nutrient growth medium and no significant temperature rise was noticed at the waveguide‐cell interface. It is strongly suggested that the cell‐killing mechanism is directly related to both the intense electric field at the cell‐waveguide interface and the penetration of the evanescent tail into the cell. Interactions which can only take place in the presence of intense electric field strengths at optical frequencies are presented as possible mechanisms involved in the cell‐killing process. Procedures are outlined for the design of waveguides capable of producing optical power densities and electric field strengths up to 10 8 W/cm 2 and 10 5 V/cm, respectively.