Abstract

We have designed and built a static tester around a commercially available polarized light microscope. This device employs two semiconductor laser diodes (at 643- and 680-nm wavelengths) for the purpose of recording small marks on various media for optical data storage and for the simultaneous monitoring of the recording process. We use one of the lasers in the single-pulse mode to write a mark on the sample and operate the other laser in the cw mode to monitor the recording process. The two laser beams are brought to coincident focus on the sample through the objective lens of the microscope. The reflected beams are sent through a polarizing beam splitter and thus divided into two branches, depending on whether they are p or s polarized. In each branch the beam is further divided into two according to the wavelength. The four beams thus produced are sent to four high-speed photodetectors, and the resulting signals are used to monitor the reflectance as well as the polarization state of the beam on reflection from the sample. We provide a comprehensive description of the tester’s design and operating principles. We also report preliminary results of measurements of phase-change, dye–polymer, and magneto-optical samples, which are currently of interest in the areas of writable and rewritable optical data storage.

© 1999 Optical Society of America

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References

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  1. T. W. McDaniel, R. H. Victora, eds., Handbook of Magneto-optical Recording (Noyes, Westwood, N.J., 1997).
  2. M. Mansuripur, The Physical Principles of Magneto-optical Recording (Cambridge U. Press, London, UK, 1995).
    [CrossRef]
  3. Reversibility of the initial decline in the reflectivity curves of Fig. 6 may be inferred from the τ = 0.25 µs curve; it was also confirmed by our numerous other short-pulse experiments on the same sample. At P2 = 4 mW and t = 100 ns the temperature rise at the center of the focused spot is estimated to be ∼300 °C, which is large enough to cause changes in the electronic band structure and consequently to modify the optical constants of the sample.
  4. S. R. Ovshinsky, “Reversible electrical switching phenomena in disordered structures,” Phys. Rev. Lett. 21, 1450–1453 (1968).
    [CrossRef]
  5. J. Feinleib, J. deNeufvile, S. C. Moss, S. R. Ovshinsky, “Rapid reversible light-induced crystallization of amorphous semiconductors,” Appl. Phys. Lett. 18, 254–257 (1971).
    [CrossRef]
  6. T. Ohta, M. Takenaga, N. Akahira, T. Yamashita, “Thermal change of optical properties in some sub-oxide thin films,” J. Appl. Phys. 53, 8497–8500 (1982).
    [CrossRef]
  7. D. Chen, G. N. Otto, F. M. Schmit, “MnBi films for magneto-optic recording,” IEEE Trans. Magn. MAG-9, 66–83 (1973).
    [CrossRef]
  8. Y. Mimura, N. Imamura, T. Kobayashi, “Magnetic properties and Curie point writing in amorphous metallic films,” IEEE Trans. Magn. MAG-12, 779–781 (1976).
    [CrossRef]
  9. S. Yonezawa, M. Takahashi, “Thermodynamic simulation of magnetic field modulation methods for pulsed laser irradiation in magneto-optical disks,” Appl. Opt. 33, 2333–2337 (1994).
    [CrossRef] [PubMed]
  10. J. J. Wrobel, A. B. Marchant, D. G. Howe, “Laser marking of organic films,” Appl. Phys. Lett. 40, 928–930 (1982).
    [CrossRef]
  11. E. Hamada, T. Fujii, Y. Takagishi, T. Ishiguro, “Recording process of recordable compact disc,” in Optical Data Storage, D. B. Carlin, D. B. Kay, eds., Proc. SPIE1663, 443–446 (1992).
    [CrossRef]

1994 (1)

1982 (2)

J. J. Wrobel, A. B. Marchant, D. G. Howe, “Laser marking of organic films,” Appl. Phys. Lett. 40, 928–930 (1982).
[CrossRef]

T. Ohta, M. Takenaga, N. Akahira, T. Yamashita, “Thermal change of optical properties in some sub-oxide thin films,” J. Appl. Phys. 53, 8497–8500 (1982).
[CrossRef]

1976 (1)

Y. Mimura, N. Imamura, T. Kobayashi, “Magnetic properties and Curie point writing in amorphous metallic films,” IEEE Trans. Magn. MAG-12, 779–781 (1976).
[CrossRef]

1973 (1)

D. Chen, G. N. Otto, F. M. Schmit, “MnBi films for magneto-optic recording,” IEEE Trans. Magn. MAG-9, 66–83 (1973).
[CrossRef]

1971 (1)

J. Feinleib, J. deNeufvile, S. C. Moss, S. R. Ovshinsky, “Rapid reversible light-induced crystallization of amorphous semiconductors,” Appl. Phys. Lett. 18, 254–257 (1971).
[CrossRef]

1968 (1)

S. R. Ovshinsky, “Reversible electrical switching phenomena in disordered structures,” Phys. Rev. Lett. 21, 1450–1453 (1968).
[CrossRef]

Akahira, N.

T. Ohta, M. Takenaga, N. Akahira, T. Yamashita, “Thermal change of optical properties in some sub-oxide thin films,” J. Appl. Phys. 53, 8497–8500 (1982).
[CrossRef]

Chen, D.

D. Chen, G. N. Otto, F. M. Schmit, “MnBi films for magneto-optic recording,” IEEE Trans. Magn. MAG-9, 66–83 (1973).
[CrossRef]

deNeufvile, J.

J. Feinleib, J. deNeufvile, S. C. Moss, S. R. Ovshinsky, “Rapid reversible light-induced crystallization of amorphous semiconductors,” Appl. Phys. Lett. 18, 254–257 (1971).
[CrossRef]

Feinleib, J.

J. Feinleib, J. deNeufvile, S. C. Moss, S. R. Ovshinsky, “Rapid reversible light-induced crystallization of amorphous semiconductors,” Appl. Phys. Lett. 18, 254–257 (1971).
[CrossRef]

Fujii, T.

E. Hamada, T. Fujii, Y. Takagishi, T. Ishiguro, “Recording process of recordable compact disc,” in Optical Data Storage, D. B. Carlin, D. B. Kay, eds., Proc. SPIE1663, 443–446 (1992).
[CrossRef]

Hamada, E.

E. Hamada, T. Fujii, Y. Takagishi, T. Ishiguro, “Recording process of recordable compact disc,” in Optical Data Storage, D. B. Carlin, D. B. Kay, eds., Proc. SPIE1663, 443–446 (1992).
[CrossRef]

Howe, D. G.

J. J. Wrobel, A. B. Marchant, D. G. Howe, “Laser marking of organic films,” Appl. Phys. Lett. 40, 928–930 (1982).
[CrossRef]

Imamura, N.

Y. Mimura, N. Imamura, T. Kobayashi, “Magnetic properties and Curie point writing in amorphous metallic films,” IEEE Trans. Magn. MAG-12, 779–781 (1976).
[CrossRef]

Ishiguro, T.

E. Hamada, T. Fujii, Y. Takagishi, T. Ishiguro, “Recording process of recordable compact disc,” in Optical Data Storage, D. B. Carlin, D. B. Kay, eds., Proc. SPIE1663, 443–446 (1992).
[CrossRef]

Kobayashi, T.

Y. Mimura, N. Imamura, T. Kobayashi, “Magnetic properties and Curie point writing in amorphous metallic films,” IEEE Trans. Magn. MAG-12, 779–781 (1976).
[CrossRef]

Mansuripur, M.

M. Mansuripur, The Physical Principles of Magneto-optical Recording (Cambridge U. Press, London, UK, 1995).
[CrossRef]

Marchant, A. B.

J. J. Wrobel, A. B. Marchant, D. G. Howe, “Laser marking of organic films,” Appl. Phys. Lett. 40, 928–930 (1982).
[CrossRef]

Mimura, Y.

Y. Mimura, N. Imamura, T. Kobayashi, “Magnetic properties and Curie point writing in amorphous metallic films,” IEEE Trans. Magn. MAG-12, 779–781 (1976).
[CrossRef]

Moss, S. C.

J. Feinleib, J. deNeufvile, S. C. Moss, S. R. Ovshinsky, “Rapid reversible light-induced crystallization of amorphous semiconductors,” Appl. Phys. Lett. 18, 254–257 (1971).
[CrossRef]

Ohta, T.

T. Ohta, M. Takenaga, N. Akahira, T. Yamashita, “Thermal change of optical properties in some sub-oxide thin films,” J. Appl. Phys. 53, 8497–8500 (1982).
[CrossRef]

Otto, G. N.

D. Chen, G. N. Otto, F. M. Schmit, “MnBi films for magneto-optic recording,” IEEE Trans. Magn. MAG-9, 66–83 (1973).
[CrossRef]

Ovshinsky, S. R.

J. Feinleib, J. deNeufvile, S. C. Moss, S. R. Ovshinsky, “Rapid reversible light-induced crystallization of amorphous semiconductors,” Appl. Phys. Lett. 18, 254–257 (1971).
[CrossRef]

S. R. Ovshinsky, “Reversible electrical switching phenomena in disordered structures,” Phys. Rev. Lett. 21, 1450–1453 (1968).
[CrossRef]

Schmit, F. M.

D. Chen, G. N. Otto, F. M. Schmit, “MnBi films for magneto-optic recording,” IEEE Trans. Magn. MAG-9, 66–83 (1973).
[CrossRef]

Takagishi, Y.

E. Hamada, T. Fujii, Y. Takagishi, T. Ishiguro, “Recording process of recordable compact disc,” in Optical Data Storage, D. B. Carlin, D. B. Kay, eds., Proc. SPIE1663, 443–446 (1992).
[CrossRef]

Takahashi, M.

Takenaga, M.

T. Ohta, M. Takenaga, N. Akahira, T. Yamashita, “Thermal change of optical properties in some sub-oxide thin films,” J. Appl. Phys. 53, 8497–8500 (1982).
[CrossRef]

Wrobel, J. J.

J. J. Wrobel, A. B. Marchant, D. G. Howe, “Laser marking of organic films,” Appl. Phys. Lett. 40, 928–930 (1982).
[CrossRef]

Yamashita, T.

T. Ohta, M. Takenaga, N. Akahira, T. Yamashita, “Thermal change of optical properties in some sub-oxide thin films,” J. Appl. Phys. 53, 8497–8500 (1982).
[CrossRef]

Yonezawa, S.

Appl. Opt. (1)

Appl. Phys. Lett. (2)

J. J. Wrobel, A. B. Marchant, D. G. Howe, “Laser marking of organic films,” Appl. Phys. Lett. 40, 928–930 (1982).
[CrossRef]

J. Feinleib, J. deNeufvile, S. C. Moss, S. R. Ovshinsky, “Rapid reversible light-induced crystallization of amorphous semiconductors,” Appl. Phys. Lett. 18, 254–257 (1971).
[CrossRef]

IEEE Trans. Magn. (2)

D. Chen, G. N. Otto, F. M. Schmit, “MnBi films for magneto-optic recording,” IEEE Trans. Magn. MAG-9, 66–83 (1973).
[CrossRef]

Y. Mimura, N. Imamura, T. Kobayashi, “Magnetic properties and Curie point writing in amorphous metallic films,” IEEE Trans. Magn. MAG-12, 779–781 (1976).
[CrossRef]

J. Appl. Phys. (1)

T. Ohta, M. Takenaga, N. Akahira, T. Yamashita, “Thermal change of optical properties in some sub-oxide thin films,” J. Appl. Phys. 53, 8497–8500 (1982).
[CrossRef]

Phys. Rev. Lett. (1)

S. R. Ovshinsky, “Reversible electrical switching phenomena in disordered structures,” Phys. Rev. Lett. 21, 1450–1453 (1968).
[CrossRef]

Other (4)

T. W. McDaniel, R. H. Victora, eds., Handbook of Magneto-optical Recording (Noyes, Westwood, N.J., 1997).

M. Mansuripur, The Physical Principles of Magneto-optical Recording (Cambridge U. Press, London, UK, 1995).
[CrossRef]

Reversibility of the initial decline in the reflectivity curves of Fig. 6 may be inferred from the τ = 0.25 µs curve; it was also confirmed by our numerous other short-pulse experiments on the same sample. At P2 = 4 mW and t = 100 ns the temperature rise at the center of the focused spot is estimated to be ∼300 °C, which is large enough to cause changes in the electronic band structure and consequently to modify the optical constants of the sample.

E. Hamada, T. Fujii, Y. Takagishi, T. Ishiguro, “Recording process of recordable compact disc,” in Optical Data Storage, D. B. Carlin, D. B. Kay, eds., Proc. SPIE1663, 443–446 (1992).
[CrossRef]

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Figures (12)

Fig. 1
Fig. 1

Diagram of the static tester built around a polarized-light microscope. The main column of the microscope, depicted at the right, contains a white-light source, a polarizer, an analyzer, a CCD camera, and an objective lens. The sample sits atop a computer-controlled XY translation stage. An electromagnet is placed below the stage for measurement of MO samples. The elements within the box include two laser diodes and the necessary optics for guiding the laser beams to the sample and back to the detectors. PBS, polarizing beam splitter; other abbreviations defined in text.

Fig. 2
Fig. 2

Measured transmission spectrum of the dichroic mirror in the wavelength range from 450 to 750 nm at 45° angle of incidence.

Fig. 3
Fig. 3

Transmission spectrum of the multilayer stack used as a beam combiner at 45° angle of incidence. The calculated curve is taken from the design parameters listed in Table 1.

Fig. 4
Fig. 4

Measured hysteresis loop of the electromagnet that sits beneath the sample in the system of Fig. 1. The Hall probe that we used to obtain this loop was placed in the narrow air gap between the magnet’s conical pole piece and the flat iron plate (not shown) in which the magnet’s external arm terminates. The horizontal axis represents the electric current applied to the coil, and the vertical axis depicts the values of the magnetic field measured by the Hall probe. The dashed curves inside the loop are the initial magnetization curves.

Fig. 5
Fig. 5

Quadrilayer stack consisting of a thin film of Ge2Sb2Te5 PC material sandwiched between two dielectric layers and capped with an aluminum alloy film. The laser beams must be focused upon the PC layer through the substrate. The results of measurements of this sample appear in Figs. 6 and 7.

Fig. 6
Fig. 6

Plots of reflectivity versus time during local crystallization of the as-deposited amorphous PC film encapsulated in the quadrilayer stack of Fig. 5. The pulsed beam from laser 2 had a peak power of 4.00 mW, but its duration τ was fixed at different values for the various curves shown. The cw power of laser 1 was fixed at 0.3 mW. Both beams were focused on the same spot on the sample through a 0.6-N.A. objective, which was corrected for the 1.2-mm thickness of the sample’s substrate.

Fig. 7
Fig. 7

Plots of reflectivity versus time during local melting and subsequent quenching of the precrystallized PC film encapsulated in the quadrilayer stack of Fig. 5. The pulsed beam from laser 2 had a peak power of 8.0 mW, but its duration τ was fixed at different values for the various curves shown. The cw power of laser 1 was fixed at 0.2 mW. Both beams were focused on the same spot on the sample through a 0.6-N.A. objective, which was corrected for the 1.2-mm thickness of the sample’s substrate.

Fig. 8
Fig. 8

Photograph of the recorded marks on a PC sample, as seen through the CCD camera. These crystalline marks were written upon an as-deposited amorphous film with 7.0-mW, 2.0-µs pulses from laser 2. The center-to-center spacing between adjacent marks is 6 µm.

Fig. 9
Fig. 9

Kerr hysteresis loops measured on a front-surface quadrilayer MO sample by the cw beam from laser 1 while laser 2 was turned off. These four loops were obtained at different values of beam power P 1 (measured at the sample’s surface). The magnetic field was scanned between ±8.1 kOe in steps of 50 Oe. The beam was focused on the magnetic layer of the sample through a 0.6-N.A. objective. The LC cell’s phase shift Δϕ was adjusted for the maximum Kerr signal, i.e., the loop height.

Fig. 10
Fig. 10

Plots of Kerr signal versus time during the process of thermomagnetic recording on the same quadrilayer MO sample as used in Fig. 9. The cw probe beam from laser 1 was set at the low power level of P 1 = 0.28 mW. The magnetic field was fixed at H = -2 kOe, and laser 2 was pulsed for a τ = 2 µs duration. The various curves shown correspond to different pulse power levels P 2, as indicated on each curve. Both laser beams were focused on the same spot on the sample through a 0.6-N.A. objective. The large bandwidth of the detector module and the small magnitude of the differential MO signal are responsible for the noisy appearance of these plots.

Fig. 11
Fig. 11

Scanning polarization micrograph of a thermomagnetically recorded domain after it has been expanded under a magnetic field just below the sample’s coercivity. Many branches appear on the periphery of the domain, and new nucleation centers develop in other regions of the sample.

Fig. 12
Fig. 12

Plots of reflectivity versus time during local melting–ablation of the dye layer of a commercial CD-R disk. The pulsed beam from laser 2 had a peak power of 3.5 mW, but its duration τ was fixed at different values for the various curves (τ = 0.5–3.5 µs in steps of 0.5 µs). The cw probe power was fixed at P 1 = 0.1 mW. Both beams were focused on the same spot on the disk through a 0.6-N.A. objective, which was corrected for the 1.2-mm thickness of the sample’s substrate.

Tables (1)

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Table 1 Design Parameters of the 29-Layer Stack Used As a Beam Combiner in the Static Laser

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