Skip to main content
Journal of Engineering and Applied Science
Download PDF

Influence of pulse-tail energy of short-pulse CO2 laser in drilling of various glasses

Journal of Engineering and Applied Science volume 70, Article number: 137 (2023) Cite this article

Abstract

In a short-pulse CO2 laser based on discharge excitation, there is a pulse tail that depends on the device configuration and operating conditions. The pulse tail is longer than the spike pulse and causes thermal effects such as a crack, heat-affected zones (HAZ), and so on. There are various types of glass having different physical constants related to heat, such as the thermal expansion coefficient and the softening point. Even if the same CO2 laser pulse is radiated onto glass, the processing results may differ depending on the glass material. Four types of glass, namely, crown glass, soda-lime glass, borosilicate glass, and synthetic quartz glass were irradiated with two types of short CO2 laser pulses, one with a large pulse tail and one with a small pulse tail, at a repetition rate of 200 Hz and a fluence per pulse of 22 J/cm2. As the processing characteristics, the ratios of the surface hole diameter and the HAZ diameter to the irradiation diameter, as well as the drilling depth, were investigated. The pulse-tail energy of the short CO2 laser pulses did not affect the surface hole diameter. In the glasses with small softening points of 740 °C or less, the pulse-tail energy of short CO2 laser pulses affected the HAZ with a large number of pulse irradiations with a total irradiation fluence of 2000 J/cm2 or more. The short CO2 laser pulses with a small tail produced a smaller HAZ than the short CO2 laser pulses with a large tail. In drilling with a large number of pulse irradiations, the short CO2 laser pulses with a small tail produced deeper drilling than the short CO2 laser pulses with a large tail. The glass material did not affect the surface hole diameter and the drilling depth. The glass material affected the HAZ.

Introduction

Many types of CO2 lasers have been widely applied in the laser industry because CO2 lasers can produce pulsed light with a pulse width of 10 ns to 1 ms or continuous wave (CW) light with high power at wavelengths in the range of 9.2  µm to 11.4 µm (mainly 9.6 µm and 10.6 µm). Processing of various materials, such as glass [1,2,3,4,5,6,7,8,9,10,11], polymer resin [12,13,14], fiber-reinforced resin [15,16,17], wood [18, 19], etc., by various CO2 lasers has been reported. In glass processing by a CO2 laser, the CO2 laser light is absorbed at the glass surface because the wavelength of a CO2 laser is 9.2 µm to 11.4 µm. CO2 lasers employ thermal processing because the pulse width of commercial CO2 lasers is 10 ns at the shortest. The heat generated by a laser pulse on a sample may depend on the laser pulse waveform, the pulse width, the fluence, and the repetition rate.

In a transversely excited atmospheric (TEA) CO2 laser, which is a short-pulse CO2 laser, the laser pulse waveform has a spike pulse with a width of about 100 ns and a pulse tail with a length of several microseconds [20,21,22,23,24]. Even in our recently developed longitudinally excited CO2 lasers, the short pulse has a spike pulse with a width of about 100 ns and a pulse tail with a length of several to several hundreds of microseconds, although a short pulse without a pulse tail can be produced [25,26,27,28,29]. Our CO2 laser controls the spike pulse width and the energy ratio of the spike pulse to the pulse tail. The pulse tail of a discharge-pumped CO2 laser is caused by a small current after the main discharge and long-lifetime resonance excitation by N2 contained in the medium gas, and the pulse tail depends on the device configuration and operating conditions. The pulse tail is longer than the spike pulse and causes thermal effects, such as a crack, a heat-affected zone (HAZ), and so on. In our previous work, a short pulse with a spike pulse width of about 250 ns, a pulse tail length of 31.4 µs, and an energy ratio of the spike pulse to the pulse tail of 1:7 to 1:92 produced a crack-less hole in a crown glass with a high thermal expansion coefficient of 100 × 10−7 /K at a repetition rate of 150 Hz to 400 Hz [11]. However, there are various types of glasses, and their physical constants related to heat, such as the thermal expansion coefficient and the softening point, are different. The stress caused by a temperature gradient produces cracks, and glass with a high thermal expansion coefficient tends to crack easily. In addition, glass with a low softening point tends to easily exhibit a HAZ. Therefore, even if the same type of CO2 laser pulse is used to irradiate different glasses, the processing results may differ depending on the glass material.

In this work, the objective is to investigate the influence of the pulse-tail energy of short-pulse CO2 laser drilling of various types of glass with thermal expansion coefficients of 100 × 10−7 /K to 5.5 × 10−7/K and softening points of 724 °C to 1600 °C. Thus, in this work, two types of short CO2 laser pulses, one with a large tail and one with a small tail, were radiated onto four types of glass with different thermal expansion coefficients and softening points, and the processing characteristics were investigated.

Experimental

Figure 1 shows the schematic diagram of the experimental setup consisting of a longitudinally excited CO2 laser, an attenuator, a lens, a stage, and a sample [25,26,27,28,29]. The CO2 laser emitted two types of short laser pulses as shown in Fig. 2. The large-tail short pulse had a spike pulse width of 450 ns, a tail length of 71 µs and an energy ratio of the spike pulse to the pulse tail of 1:31. The small-tail short pulse had a spike pulse width of 570 ns, a tail length of 35 µs and an energy ratio of the spike pulse to the pulse tail of 1:8. In both laser pulses, the wavelength was 10.6 µm, the repetition rate was 200 Hz, and the beam profile was a circular Gaussian-like shape with a correlation coefficient of 0.98. The focal length of the lens was 38.1 mm, the numerical aperture (NA) was 0.16, and the focal spot size was 230 µm. The sample surface was fixed at the focal plane. The fluence per pulse of whole laser pulse waveforms was adjusted by the attenuator to 22 J/cm2 in both laser pulse waveforms with energy ratios of 1:31 and 1:8. The samples were crown glass with a thermal expansion coefficient (CTE) of 100 × 10−7/K, a softening point (SP) of 724 °C and a thickness of 1.1 mm, soda-lime glass with a CTE of 87 × 10−7 /K, a SP of 740 °C and a thickness of 1.2 mm, low expansion borosilicate glass with a CTE of 33 × 10−7/K, a SP of 820 °C and a thickness of 1.1 mm, and synthetic quartz glass with a CTE of 5.5 × 10−7/K, a SP of 1600 °C and a thickness of 2.0 mm. As the thermal expansion coefficient decreased, the softening point tended to increase. In CO2 laser processing of glass with a large thermal expansion coefficient, generally, various treatments before, during, or after irradiation for suppression of crack production have been reported [4,5,6,7]. However, in the present work, such treatments were not used to investigate the HAZ.

Fig. 1
figure 1

Schematic diagram of experimental setup

Full size image
Fig. 2
figure 2

Laser pulse waveforms. Red and blue lines represent laser pulse waveforms with energy ratios of 1:31 and 1:8, respectively. a Magnified time scale of spike pulse. b Overall waveform

Full size image

Results and discussion

In this work, none of the samples exhibited cracks. Figure 3 shows an image of crown glass irradiated with 200 large-tail short pulses with an energy ratio of 1:31. The irradiation diameter was 230 µm, and the total irradiation fluence was 4400 J/cm2. The surface hole diameter as shown in Fig. 3a was 144 µm, and the ratio of the surface hole diameter to the irradiation diameter was 61.1%. The HAZ diameter as shown in Fig. 3b was 425 µm, and the ratio of the HAZ diameter to the irradiation diameter was 181%. The drilling depth as shown in C of Fig. 3c was 854 µm.

Fig. 3
figure 3

Image of crown glass irradiated with 200 short pulses with a large tail a Surface image. a and b show surface hole diameter and HAZ diameter, respectively. b Side image. c shows the drilling depth

Full size image

Figure 4 shows the dependence of the ratio of the surface hole diameter to the irradiation diameter on the total irradiation fluence, that is the fluence per single pulse multiplied by the number of irradiation pulses in crown glass with a CTE of 100 × 10−7/K and a SP of 724 °C, soda-lime glass with a CTE of 87 × 10−7/K and SP of 740 °C, low expansion borosilicate glass with a CTE of 33 × 10−7/K and a SP of 820 °C, and synthetic quartz glass with a CTE of 5.5 × 10−7/K and a SP of 1600 °C. In this work, the results were presented using the ratio of the surface hole diameter to the irradiation diameter to illustrate the relationship between the irradiation diameter and the surface hole diameter. Figure 4a presents the results obtained with the large-tail short laser pulse with the energy ratio of the spike pulse to the pulse tail of 1:31, and Fig. 4b presents the results obtained with the small-tail short laser pulse the energy ratio of 1:8. In the laser pulse waveform with the energy ratio of 1:31, the ratio of the surface hole diameter increased slightly with the increase of the total irradiation fluence but did not depend on the glass material. The average ratio was about 59.8%. In the laser pulse waveform with the energy ratio of 1:8, the ratio of the surface hole diameter did not depend on the total irradiation fluence or the glass material and was constant at about 59.8%.

Fig. 4
figure 4

Dependence of ratio of surface hole diameter to irradiation diameter on total irradiation fluence. Circles, squares, diamonds, and triangles represent crown glass, soda-lime glass, borosilicate glass, and synthetic quartz glass, respectively. a Laser pulse waveform with an energy ratio of 1:31. b Laser pulse waveform with an energy ratio of 1:8

Full size image

Figure 5 shows the dependence of the ratio of the HAZ diameter to the irradiation diameter on the total irradiation diameter in crown glass with a CTE of 100 × 10−7 /K and a SP of 724 °C, soda-lime glass with a CTE of 87 × 10−7/K and SP of 740 °C, low expansion borosilicate glass with a CTE of 33 × 10−7/K and a SP of 820 °C, and synthetic quartz glass with a CTE of 5.5 × 10−7 /K and a SP of 1600 °C. In this work, the results were presented using the ratio of the HAZ diameter to the irradiation diameter to illustrate the relationship between the irradiation diameter and the HAZ diameter. Figure 5a presents the results obtained with the large-tail short laser pulse with the energy ratio of the spike pulse to the pulse tail of 1:31, and Fig. 5b presents the results obtained with the small-tail short laser pulse with the energy ratio of 1:8. In both laser pulse waveforms with the energy ratios of 1:31 and 1:8, the ratio of the HAZ diameter increased with the increase of the total irradiation fluence, and the decrease of the softening point of the glass. The ratio of the HAZ diameter produced by the laser pulse waveform with the energy ratio of 1:31 was larger than that produced by the laser pulse waveform with the energy ratio of 1:8. In particular, in a glass material with a low softening point, the difference became significant when the total irradiation fluence was over 2000 J/cm2.

Fig. 5
figure 5

Dependence of ratio of HAZ diameter to irradiation diameter on total irradiation fluence. Circles, squares, diamonds, and triangles represent crown glass, soda-lime glass, borosilicate glass, and synthetic quartz glass, respectively. a Laser pulse waveform with an energy ratio of 1:31. b Laser pulse waveform with an energy ratio of 1:8

Full size image

Figure 6 shows the dependence of the drilling depth on the total irradiation diameter in crown glass with a CTE of 100 × 10−7/K and a SP of 724 °C, soda-lime glass with a CTE of 87 × 10−7/K and SP of 740 °C, low expansion borosilicate glass with a CTE of 33 × 10−7/K and a SP of 820 °C, and synthetic quartz glass with a CTE of 5.5 × 10−7/K and a SP of 1600 °C. Figure 6a presents the results obtained with the large-tail short laser pulse with the energy ratio of the spike pulse to the pulse tail of 1:31, and Fig. 6b presents the results obtained with the small-tail short laser pulse with the energy ratio of 1:8. In both laser pulse waveforms with the energy ratios of 1:31 and 1:8, the drilling depth increased with the increase of the total irradiation fluence but did not depend on the glass material. At a total irradiation fluence of about 220 J/cm2, the drilling depth produced by the laser pulse waveform with the energy ratio of 1:31 was almost the same as that produced by the laser pulse waveform with the energy ratio of 1:8 and was about 323 µm. However, at a total irradiation fluence of 500 J/cm2 or more, the drilling depth produced by the laser pulse waveform with the energy ratio of 1:31 was smaller than that produced by the laser pulse waveform with the energy ratio of 1:8. This may be attributed to the fluence of the spike pulse part of the laser pulse waveform. In this work, the fluence per single pulse of whole laser pulse waveforms was 22 J/cm2 in both laser pulse waveforms with the energy ratios of 1:31 and 1:8. Therefore, the fluence per pulse of the spike pulse parts was 0.69 J/cm2 and 2.44 J/cm2 in the laser pulse waveforms with the energy ratios of 1:31 and 1:8, respectively. In drilling with a large number of irradiation pulses, the fluence per pulse of the spike pulse part affected the drilling depth.

Fig. 6
figure 6

Dependence of drilling depth on total irradiation fluence. Circles, squares, diamonds, and triangles represent crown glass, soda-lime glass, borosilicate glass, and synthetic quartz glass, respectively. a Laser pulse waveform with an energy ratio of 1:31. b Laser pulse waveform with an energy ratio of 1:8

Full size image

Conclusions

Two types of short CO2 laser pulses, with a large or small tail, were radiated onto four types of glass with thermal expansion coefficients of 100 × 10−7/K to 5.5 × 10−7/K and softening points of 724 °C to 1600 °C at a repetition rate of 200 Hz and a fluence per pulse of 22 J/cm2, and the processing characteristics, in terms of the ratios of the surface hole diameter and the HAZ diameter to the irradiation diameter, as well as the drilling depth, were investigated. The surface hole diameter did not depend on the pulse-tail energy of the short CO2 laser pulse and the glass material. The ratio was about 59.8%. In glass with a large softening point of 820 °C or more, the HAZ was not affected by the pulse-tail energy of a short CO2 laser pulse. In glass with a small softening point of 740 °C or less, the HAZ produced by the short CO2 laser pulse with a small tail at a total irradiation fluence of 2000 J/cm2 or more was smaller. The drilling depth increased with the increase of the total irradiation fluence but did not depend on the glass material. In drilling with a large number of irradiation pulses, the fluence per pulse of the spike pulse part affected the drilling depth. Therefore, in glass processing by a short-pulse CO2 laser, the pulse-tail energy of the laser pulse waveform is an important parameter to be considered. However, with a small total irradiation fluence produced by a small number of irradiation pulses, the pulse-tail energy of the laser pulse waveform does not affect the results of glass drilling.

Availability of data and materials

The datasets generated during the current study are available from the corresponding author on reasonable request.

Abbreviations

CO2 :

Carbon dioxide

HAZ:

Heat affected zone

CW:

Continuous wave

TEA:

Transversely excited atmospheric

NA:

Numerical aperture

CTE:

Thermal expansion coefficient

SP:

Softening point

References

  1. Ogura H, Yoshida Y (2003) Hole Drilling of Glass Substrates with a CO2 Laser. Jpn J Appl Phys 42:2881–2886

    Article  Google Scholar 

  2. Nowak KM, Baker HJ, Hall DR (2015) Analytical model for CO2 laser ablation of fused quartz. App Optics 54:8653–8663

    Article  Google Scholar 

  3. Zhang C, Zhang L, Jiang X, Jia B, Liao W, Dai R, Chen J, Yuan X, Jiang X (2020) Influence of pulse length on heat affected zones of evaporatively-mitigated damages of fused silica optics by CO2 laser. Opt Laser Eng 125:105857

    Article  Google Scholar 

  4. Brusberg L, Queisser M, Gentsch C, Schroder H, Lang KD (2012) Advances in CO2-Laser Drilling of Glass Substrates. Phys Procedia 39:548–555

    Article  Google Scholar 

  5. Chung CK, Lin SL (2010) CO2 laser micromachined crackles through holes of Pyrex 7740 glass. Int J Mach Tools Manuf 50:961–968

    Article  Google Scholar 

  6. Ali A, Sundaram M (2018) Drilling of crack free micro holes in glass by chemo-thermal micromachining process. Precis Eng 54:33–38

    Article  Google Scholar 

  7. Chung CK, Lin SL, Wang HY, Tan TK, Tu KZ, Lung HF (2013) Fabrication and simulation of glass micromachining using CO2 laser processing with PDMS protection. Appl Phys A 113:501–507

    Article  Google Scholar 

  8. Kim T, Kwan KK, Chu CN, Song KY (2020) Experimental investigation on CO2 laser-assisted micro-slot milling characteristics of borosilicate glass. Precis Eng 63:137–1477

    Article  Google Scholar 

  9. Perrone E, Cesaria M, Zizzari A, Bianco M, Ferrara F, Raia L, Guarino V, Cuscuna M, Mazzeo M, Gigli G, Moroni L, Arima V Potential of CO2-laser processing of quartz for fast prototyping of microfluidic reactors and templates for 3D cell assembly over large scale. Mater. Today Bio 12:100163.

  10. Furumoto T, Hashimoto Y, Ogi H, Kawabe T, Yamaguchi M, Koyano T, Hosokawa, (2021) A CO2 laser cleavage of chemically strengthened glass. J Mater Process Technol 289:116961

    Article  Google Scholar 

  11. Rahaman ME, Uno K (2022) Crown glass drilling by short-pulse CO2 laser with tunable pulse tail. Lasers Manuf Mater Process 9:72–80

    Article  Google Scholar 

  12. Prakash S, Kumar S (2021) Determining the suitable CO2 laser based technique for microchannel fabrication on PMMA. Opt Laser Technol 139:107017

    Article  Google Scholar 

  13. Kaba AM, Jeon H, Park A, Yi K, Baek S, Park A, Kim D (2021) Cavitation-microstreaming-based lysis and DNA extraction using a laser-machined polycarbonate microfluidic chip. Sens Actuators B Chem 346:130511

    Article  Google Scholar 

  14. Abdulwahab AE, Hubeatir KA, Imhan KI (2022) Optimization of PC micro-drilling using a continuous CO2 laser: am experimental and theoretical comparative study. J Eng Appl Sci 69:98

    Article  Google Scholar 

  15. Salama A, Li L, Mativenga P, Whitehead D (2016) TEA CO2 laser machining of CFRP composite. Appl Phys A 122:497

    Article  Google Scholar 

  16. Endo M, Araya N, Kurokawa Y, Uno K (2016) Anomalous enhancement of drilling rate in carbon fiber reinforced plastic using azimuthally polarized CO2 laser. Laser Phys 26:096001

    Article  Google Scholar 

  17. Solati A, Hamedi M, Safarabadi M (2019) Comprehensive investigation of surface quality and mechanical properties in CO2 laser drilling of GFRP composites. Int J Adv Manuf Technol 102:791–808

    Article  Google Scholar 

  18. Nath S, Waugh DG, Ormondroyd GA, Spear MJ, Pitman AJ, Sahoo S, Curling SF, Mason P (2020) CO2 laser interactions with wood tissues during single pulse laser-incision. Opt Laser Technol 126:106069

    Article  Google Scholar 

  19. Guo X, Deng M, Hu Y, Wang Y, Ye T (2021) Morphology, mechanism and kerf variation during CO2 laser cutting pine wood. J Manuf Process 68:13–22

    Article  Google Scholar 

  20. Menyuk N, Moulton PF (1980) Development of a high-repetition-rate mini-TEA CO2 laser. Rev Sci Instrum 51:216

    Article  Google Scholar 

  21. Karapuzikov AI, Malov AN, Sherstov IV (2000) Tunable TEA CO2 laser for long-range DIAL lidar. Infrared Phys Technol 41:77–85

    Article  Google Scholar 

  22. Wu J, Zhang Z, Wang D, Liu S, Tang Y, Tan R, Zhang K, Wan C (2007) Novel long-pulse TE CO2 laser excited by pulser-sustainer discharge. Opt Laser Technol 39:701–704

    Article  Google Scholar 

  23. Bellecci C, Gaudio P, Martellucci S, Penco E, Richetta M (2005) Active clipping system for transversely excited CO2 lasers. Rev Sci Instrum 76:026115

    Article  Google Scholar 

  24. Hurst N, Harilal SS (2009) Pulse shaping of transversely excited atmospheric CO2 laser using a simple plasma shutter. Rev Sci Instrum 80:035101

    Article  Google Scholar 

  25. Uno K, Jitsuno T (2018) Control of laser pulse waveform in longitudinally excited CO2 laser by adjustment of excitation circuit. Opt Laser Technol 101:195–201

    Article  Google Scholar 

  26. Uno K, Jitsuno T (2018) Control of laser pulse waveform in longitudinally excited CO2 laser by adjustment of gas medium. Proc SPIE 10811:1081111

    Google Scholar 

  27. Uno K, Li J, Goto H, Jitsuno T (2018) Longitudinally excited CO2 laser with short laser pulse and high quality beam. Proc SPIE 10518:105181Y

    Google Scholar 

  28. Sakamoto K, Uno K, Jitsuno T (2019) Longitudinally excited CO2 laser with a spike pulse width of 100 ns to 300 ns. Proc SPIE 10898:108980U

    Google Scholar 

  29. Uno K, Yanai K, Watarai S, Kodama Y, Yoneya K, Jitsuno T (2022) 1 kHz Oscillation of short-pulse CO2 laser pumped by longitudinal discharge without pre-ionization. Opt Laser Technol 152:108174

    Article  Google Scholar 

Download references

Acknowledgements

This research was partially supported by the Japan Science and Technology Agency for A-STEP, AS3015041S. The authors wish to thank Yoshihito Baba in our group.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Author information

Authors and Affiliations

  1. Integrated Graduate School of Medicine, Engineering, and Agricultural Sciences, University of Yamanashi, Yamanashi, Japan

    Kazuyuki Uno & Yasushi Kodama

  2. Seidensha Electronics Co., Ltd. of Japan, 2-2-17 Nishi-Nippori, Arakawa, Tokyo, 116-0013, Japan

    Yasushi Kodama & Kazuyuki Yoneya

Authors
  1. Kazuyuki Uno
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Yasushi Kodama
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Kazuyuki Yoneya
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

All authors have contributed to this research. The conception of the study, data collection, and manuscript draft were done by KU. The acquisition and material preparation were done by YK and KY. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Kazuyuki Uno.

Ethics declarations

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Uno, K., Kodama, Y. & Yoneya, K. Influence of pulse-tail energy of short-pulse CO2 laser in drilling of various glasses. J. Eng. Appl. Sci. 70, 137 (2023). https://doi.org/10.1186/s44147-023-00311-8

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s44147-023-00311-8

Keywords