Research of a laser diode from a DVD drive (Ilya Samoletov and Anastasia Petrova, 10th grade students)

The relevance of research is that there is an idea to use laser diodes from a DVD drive instead of expensive industrial lasers to study the phenomena of wave and coherent optics in a school laboratory.

Purpose of the study – to find and implement conditions for stable and sustainable generation of a laser diode in a single-frequency mode for use in holographic experiments.

Tasks:

1. To study the coherent properties of radiation of a laser diode with a radiation power of 40-120 mW depending on its operating modes;

2. Measure the wavelength of the laser and the coherence length of its radiation;

3. Find the conditions for stable and sustainable laser generation in single-frequency mode;

4. Develop a method for adjusting the laser diode modes in a stable single-frequency mode;

5. Design and manufacture an experimental holographic setup based on a laser diode;

6. Make a hologram using a laser diode as a source of coherent radiation.

Object of study – semiconductor laser diode.

Subject of study – coherent properties of a laser diode.

Research hypothesis:

To use a laser diode in holography, it is necessary to provide it with a single-frequency generation mode. To do this, it is necessary to find the optimal range of supply current and temperature. Most red-emitting semiconductor lasers have a coherence length of about 3–5 mm. But for some laser diodes, it is possible to select the supply current and temperature values ​​at which conditions for single-frequency generation arise, and the coherence length can reach tens of centimeters.[1]

Features of laser diodes

A laser diode is a nonlinear electrical element, and Ohm's law does not apply to it. Therefore, it requires control not by voltage, but by current. Depending on its power, a laser diode consumes 100 – 400 mA.

The main advantages of laser diodes (see Fig. 1) are their low power supply voltage (<1-3 V), the highest efficiency (up to 80%) among other types of lasers, and durability (up to 100,000 hours). In a semiconductor active medium, the gain can reach very high values ​​(up to 10,000/cm), due to which the dimensions of semiconductor lasers are extremely small.

The main factor leading to the restructuring of the radiation generation frequency is the change, together with the temperature and current, of the position of the maximum of the gain line of the active medium. According to the measurements, the change in wavelength depending on the temperature is in the range of 0.18 – 0.22 nm/°C. At the same time, the width of many temperature ranges in which the single-frequency mode is realized is 1.5–2°C, and in some cases even more.[2]

[1] Dvortsov D.V., Parfenov V.A. Spectral characteristics of single-frequency mode of operation of laser diodes. Scientific instrument making. – V.24. No.3, 2014. P. 42-48.

[2] Akilov A.A., Shevtsov M.K. Holography for the Inquisitive: A Book for School-Age Researchers. 2017. P. 206.

Dependence of the HL-6358 laser generation frequency on temperature (shaded areas correspond to the multi-frequency generation mode, and for stabilization you can select a temperature in the range of 23.5 – 25.5 °C).

During the study of the laser diode, the following works were carried out and positive results were obtained:

1. In order to determine the conditions for single-frequency generation, the laser diode (1) had to be stabilized not only by the pump current, but also by the temperature of the miniature resonator using a Peltier element (3).

. Laser diode stabilization circuit.

An experimental setup was assembled.

Optical scheme of the experimental setup.

LD – laser diode;

F1 and F2 are the focal lengths of lenses L1 and L2;

FPI – Fabry-Perot interferometer;

CCD – 18×24 mm camera matrix.

1. The conditions of the single-frequency radiation mode of the laser diode are visually determined by the width of the interference band;

2. The wavelength, spectrum width and coherence length of the laser diode radiation were calculated based on the IFP pattern;

1. The experimental holograms were recorded.

Photo 4. Setup for recording an experimental reflection hologram.

1. Laser diode with thermal stabilization device;

2. Photographic plate PFG – 03M;

3. An object;

4. Laboratory stand.

Image reconstructed from a hologram recorded using the Denisyuk scheme. Hologram exposure is 15 seconds. Laser diode temperature is 22.5 degrees Celsius, current is 111 mA.

1. A design for an amateur installation for holographic experiments is proposed.

The designs of the tube installations, similar to those shown in the figures, allow the most diverse configurations to be assembled with sufficient rigidity for recording holograms.

1 – Posts with a diameter of 25 mm and a length of 600 mm.
2 – Ties with a diameter of 25 mm and a length of 200 mm.
3 – Console with a diameter of 25 mm and a length of 500 mm.
4 – Base with a diameter of 25 mm and a length of 800 mm.
5 – Holder for holographic photographic material, 25 mm in diameter and 150 mm in length.
6 – Mirror holder for recording Leith-Upatnieks holograms with a diameter of 25 mm and a length of 200 mm.
7 – Mirror holder with external reflective coating.
8 – Object table 170×300 mm made of 15 mm thick chipboard.
9 – Laser diode holder with cooling radiator.
10 – Mirror with external reflective coating.

Conclusion

The purpose of our research – to find and provide conditions for stable and sustainable generation of a laser diode in a single-frequency mode for holography – was completed. Based on the analysis of the results of the conducted studies of laser diode radiation, we selected the conditions for the most stable single-frequency generation of radiation:

· Stabilized current – ​​111 mA.

· Stabilized temperature – 21.5 degrees Celsius or 1724 c.u.

The hypothesis of our study has been proven experimentally. The measured parameters of the laser diode radiation coincided with the results of the experimental verification. It has been proven that holograms can be successfully obtained using a laser diode. Laser diodes from DVD drives are available to everyone, which allows creating holographic installations in school laboratories.

The authors express their gratitude to Aleksandr Anatolyevich Akilov for assistance in the experimental part of the work, as well as to Galina Vasilyevna Zhus, Associate Professor of the Physics Department of the Yaroslavl Pedagogical University named after K.D. Ushinsky, for providing laboratory space and equipment.

List of references:

1. Akilov A.A., Shevtsov M.K. Holography for the Inquisitive: A Book for School-Age Researchers. 2017. P. 206.

2. Baklitsky V.K., Yuryev A.H. Optical holography / Ed. G. Caulfield. Translated from English, – T. 1-2, M., 1982. P. 736.

3. Born M., Wolf E. Fundamentals of Optics. M.: Nauka, 1973. P. 719.

4. Dvortsov D.V., Parfenov V.A. Single-frequency mode of operation of laser diodes // Scientific and technical bulletins of SPbSPU. Phys. and Mathematics. Sciences. – Vol. 170, Issue 2. 2013, pp. 89–96.

5. Dvortsov D.V., Parfenov V.A. Spectral characteristics of single-frequency mode of operation of laser diodes. Scientific instrument making. – V.24. No.3, 2014. P. 42-48.

6. Zaidel A.N., Ostrovskaya G.V., Ostrovsky Yu.I. Technique and practice of spectroscopy. M.: Nauka, 1976. P. 392.

7. Komar V.G., Serov O.B. Fine holography and holographic cinematography. Moscow: Art, 1987. P. 288.

8. Malyshev V.I. Introduction to experimental spectroscopy. Moscow: Nauka, 1979. P. 480.

9. Strong D. Practice of a modern physical laboratory. / Translated from English. M., L.: OGIZ, State Publishing House of Technical and Theoretical Literature, 1948. P. 444.

Union M. Introduction to Holography. / Translated from English by A.N. Kondrashova / Edited and with a foreword by A.I. Larkin. Moscow: Mir, 1980. P. 191.