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Laser-induced white emission (LIWE) is a broadband light in the visible spectral range. This phenomenon was reported for the first time by Jiwei Wang and Peter Tanner in 2010 for fully concentrated lanthanide oxides in vacuum, excited by a focused beam of infrared laser diode operating in continuous wave (CW) mode.[1] The white light emission intensity is exponentially dependent on excitation power density and pressure surrounding the samples. It was found that light emission is assisted by photocurrent generation and hot electron emission.

Outline

In 2010, Tanner and Wang demonstrated an innovative method of white light generation from lanthanide materials located in strictly defined conditions, by exciting them with a concentrated beam from an infrared (IR) laser diode.[1] Most importantly, this emission is characterized by a wide band covering the entire visible range, in contrast to light sources known so far, which generate white light by mixing several spectral lines. The discovery was interesting enough to attract the attention of many research groups around the world. Intensive work has begun to explore the mechanism responsible for generating this type of emission. As a result, the number of scientific publications on broadband white luminescence has been steadily increasing since 2010.[2]

Materials capable of LIWE generation

Figure 1. Power dependence of LIWE upon IR excitation.

The broadband, laser-induced white emission was reported in a number of different materials. Most common are inorganic hosts. These may be:

with lanthanide or transition (Cr3+:Y3A5O12,[22] CaCuSiO4O10,[23] Gd3Ga5O12:Cr3+[22]) metal ions.

There are also reports in the literature considering oxide matrices containing gold (Nd2O3/Au,[24] Yb2O3/Au[25] ) or silver (Ag-SiO2-Er2O3[26]) in their structure. Carbon-based materials (graphene ceramics,[27] graphene foam,[28][29] μ-diamonds[30]) or other organic ([(RMSn)(PhSn)3S6] with RM = [(Et3P)3Ag],[(Me3P)3Au],[31] [(RSn)4S6] with R = 4-(CH2=CH)–C6H4[32]) complexes undoped and doped with lanthanide ions ([YbL3]0.7[TbL3]0.3 with L = pentafluorophenyl[33]) are another relevant group of compounds. All of these materials exhibit very intense warm white light in a range of 400-800 nm.

Impact of excitation power

The LIWE generation process is non-linear and strongly depends on the excitation power density.[34][35][36][2] An increase in population power density (P) leads to a slight increase in white emission intensity (I) until a certain excitation threshold value is reached. Then, the increase in LIWE intensity is drastic (see Fig. 1). The dependence of intensity on power is described by the formula: I ∝ PN, where N is the number of near infrared photons absorbed for LIWE generation.[37] The characteristics of power dependence is not always the same and may vary depending on the tested material. In the literature some papers can be found where the increase in intensity is reported and is supported by two thresholds.[38][39][23] The emission intensity increases to a certain value of pumping power, then decreases, then increases again. According to author of this publication, it could be related with regular anti-Stokes photoluminescence, heat collection and LIWE generation, respectively. Sometimes such behavior may be caused by the presence of lanthanide ions in the investigated host due to their effective absorption of radiation used to generate LIWE.[40] It is worth to notice that the parameter N depends on the excitation wavelength.

Impact of ambient pressure

The atmospheric pressure strongly influences the LIWE intensity.[1][41] Usually, under reduced pressure conditions the intensity of white luminescence is very high due to the fact that the sample temperature is increased as a result of irradiation with a concentrated beam of the IR laser diode.[15][37] The increase in pressure causes the intensity (I0) is constant up to the threshold above which there is a sharp reduction in LIWE (see Fig. 2). Depending on the tested material, its luminescence may be completely quenched at atmospheric pressure. Such behavior is well described by heat dissipation model according to following formula: Iem = I0∙exp(-p/p0), where p0 is a critical magnitude of ambient pressure above which the luminescence intensity decreases.

Figure 2. Pressure dependence of LIWE upon IR excitation.

Sample temperature

Taking into account that broadband LIWE occurs upon illumination of the focused beam of infrared laser diode, it seems necessary to determine the sample temperature during the experiment. Several approaches to achieving this goal can be found in the literature. First is to use a thermal camera. Results obtained using this technique indicate that the sample temperature is below 1000 °C.[39][4][34][42] However it should be kept in mind, that the principle of this device is to determine the temperature from the sample surface, from a small point arising as a result of irradiation with a laser beam. Therefore, the measurement may be inaccurate, because the temperature of the sample in the entire volume may be different from the temperature determined from a single, small point on the surface. To define the sample temperature during the LIWE generation process, temperature markers in the form of up-conversion materials can be used.[43] The sample temperature values determined using this method are similar to those obtained with a thermal camera. The third approach is to fit the spectral curve using Plank's law to determine the temperature of the sample during exposure.[44] Results obtained using this method show values over 2000 °C.

Laser-induced photocurrent

The LIWE phenomenon is accompanied by efficient photocurrent generation and hot electron emission. It was found that no effects were observed for the pumping power density below the LIWE generation threshold (1 W).[37] However, above this threshold the conductivity increases with the excitation power. The conductivity for low frequencies (near DC) usually increases by several orders of magnitude after exposure of the sample with the maximum power of the excitation diode compared to the sample in the dark.[15][40] The effects associated with photoconductivity found in the materials studied so far can be explained using the hopping mechanism. Similar tendency of photoelectric phenomena can be observed in other host reported in literature.[45]

Mechanisms

The broadband anti-Stokes white emission is observed from many different materials. However, to date, there is no unambiguous model that should be used for its interpretation. Some scientists assume that LIWE is a thermal process. In this case, it is natural to use the black body radiation (BBR) model to describe this phenomenon.[1][34] In general, the theory of BBR assumes that objects heated to a sufficiently high temperature will emit white light. This means that its emission spectrum strongly depends on temperature and their curve course, which is comparable to the course of LIWE, can be well fitted using Planck’s law. Moreover, usually shift of the emission maximum with increasing sample temperature (with pumping power) is observed according to the Wien's law. This suggests that the applied model is correct. Unfortunately, often the sample temperature value obtained from fitting the emission spectrum is higher than the melting point of the material.[2] This raises doubts about the validity of the BBR model.

For this reason, scientists have started research on alternative mechanisms explaining generation of the broadband anti-Stokes white luminescence. One of them assumes formation of RE2+-CT clusters as a result of multiphoton absorption process.[4][46][47] However, many further experimental and theoretical investigations led to modification of this model. It involves ionization of the host as a consequence of its illumination with a concentrated beam of an IR laser diode. In result, free electrons in the conductivity band (CB) arise. They combine with the ions already located in CB to form pairs between ions with different degrees of oxidation states. As a consequence, the intervalence charge transfer (IVCT) transitions appeared resulting in LIWE generation.[37][48][40]

Another approach presented for inorganic materials considers the creation of oxygen vacancies due to thermal effects caused by the increased sample temperature, as a result of irradiation with a concentrated IR laser beam.[26][49][14] Then, excited electrons are captured from the excited levels of the host by oxygen vacancies through tunneling process. Subsequently, the electrons return to the valence band via radiation transitions. In case of organic materials, scientists proposed a mechanism closely related to the size of the HOMO-LUMO gap and the morphology of analyzed compound.[50] They report that irradiation of the sample by near infrared (NIR) CW laser diode causes excitation of electrons located near Fermi level. Due to the fact that their energy is below HOMO-LUMO gap, the kind of ligands strongly influences on the emission energy. It was found that carbon based materials also show the ability to generate LIWE under strong excitation. Recently reported mechanism assumes ionization of the graphene associated with intense NIR excitation, which leads to a temporary disturbance of the electronic order of its ground state.[27] In consequence, hybridization of carbon atoms changes from sp2 to sp3 resulting in opening of the graphene band gap and finally generating LIWE.[28]

References

  1. ^ a b c d Wang, Jiwei; Tanner, Peter A. (2010-01-27). "Upconversion for White Light Generation by a Single Compound". Journal of the American Chemical Society. 132 (3): 947–949. doi:10.1021/ja909254u. ISSN 0002-7863. PMID 20025211.
  2. ^ a b c Wu, Jianhong; Zheng, Guojun; Liu, Xiaofeng; Qiu, Jianrong (2020). "Near-infrared laser driven white light continuum generation: materials, photophysical behaviours and applications". Chemical Society Reviews. 49 (11): 3461–3483. doi:10.1039/C9CS00646J. ISSN 0306-0012. PMID 32338256. S2CID 216555927.
  3. ^ Xu, Sai; Zhu, Yongsheng; Xu, Wen; Dong, Biao; Bai, Xue; Xu, Lin; Miao, Chuang; Song, Hongwei (2012-09-11). "Observation of Ultrabroad Infrared Emission Bands in Er$_{2}$O$_{3}$, Pr$_{2}$O$_{3}$, Nd$_{2}$O$_{3}$, and Sm$_{2}$O$_{3}$ Polycrystals". Applied Physics Express. 5 (10): 102701. doi:10.1143/APEX.5.102701. ISSN 1882-0778. S2CID 93715195.
  4. ^ a b c Strek, W.; Marciniak, L.; Bednarkiewicz, A.; Lukowiak, A.; Wiglusz, R.; Hreniak, D. (2011-07-18). "White emission of lithium ytterbium tetraphosphate nanocrystals". Optics Express. 19 (15): 14083–92. Bibcode:2011OExpr..1914083S. doi:10.1364/OE.19.014083. ISSN 1094-4087. PMID 21934770.
  5. ^ Marciniak, L.; Tomala, R.; Stefanski, M.; Hreniak, D.; Strek, W. (March 2016). "Laser induced broad band anti-Stokes white emission from LiYbF4 nanocrystals". Journal of Rare Earths. 34 (3): 227–234. doi:10.1016/S1002-0721(16)60018-2.
  6. ^ Strek, Wieslaw; Marciniak, Lukasz; Hreniak, Dariusz; Lukowiak, Anna (2012-01-15). "Anti-Stokes bright yellowish emission of NdAlO 3 nanocrystals". Journal of Applied Physics. 111 (2): 024305–024305–6. Bibcode:2012JAP...111b4305S. doi:10.1063/1.3674272. ISSN 0021-8979.
  7. ^ Silva Filho, C. I.; Oliveira, A. L.; Pereira, S. C. F.; de Sá, Gilberto F.; da Luz, L. L.; Alves, S. (2019). "Bright thermal (blackbody) emission of visible light from LnO 2 (Ln = Pr, Tb), photoinduced by a NIR 980 nm laser". Dalton Transactions. 48 (8): 2574–2581. doi:10.1039/C8DT04649B. ISSN 1477-9226. PMID 30644485. S2CID 58585283.
  8. ^ Bilir, G.; Ozen, G.; Collins, J.; Cesaria, M.; Di Bartolo, Baldassare (August 2014). "Unconventional Production of Bright White Light Emission by Nd-Doped and Nominally Un-Doped Y2O3 Nano-Powders". IEEE Photonics Journal. 6 (4): 2201211. doi:10.1109/JPHOT.2014.2339312. S2CID 39252650.
  9. ^ Erdem, Murat; Eryurek, Gonul; Di Bartolo, Baldassare (November 2015). "Change of spectral output with pressure and white light generation in nanoscale Yb3+:Y2Si2O7". Optical Materials. 49: 90–93. Bibcode:2015OptMa..49...90E. doi:10.1016/j.optmat.2015.08.027.
  10. ^ González, Federico; Khadka, Rabindra; López-Juárez, Rigoberto; Collins, John; Di Bartolo, Baldassare (June 2018). "Emission of white-light in cubic Y4Zr3O12:Yb3+ induced by a continuous infrared laser". Journal of Luminescence. 198: 320–326. Bibcode:2018JLum..198..320G. doi:10.1016/j.jlumin.2018.02.053. S2CID 104042973.
  11. ^ Wang, Junxin; Ming, Tian; Jin, Zhao; Wang, Jianfang; Sun, Ling-Dong; Yan, Chun-Hua (December 2014). "Photon energy upconversion through thermal radiation with the power efficiency reaching 16%". Nature Communications. 5 (1): 5669. Bibcode:2014NatCo...5.5669W. doi:10.1038/ncomms6669. ISSN 2041-1723. PMID 25430519.
  12. ^ Tomala, R.; Gerasymchuk, Y.; Hreniak, D.; Legendziewicz, J.; Strek, W. (2020-01-02). "The Influence of Excitation Density on Laser Induced White Lighting of Wide-Band-Gap Semiconductor ZnSe:Yb Polycrystallite Ceramics". ECS Journal of Solid State Science and Technology. 9 (1): 016020. Bibcode:2020JSSST...9a6020T. doi:10.1149/2.0362001JSS. ISSN 2162-8777.
  13. ^ Bilir, Gokhan; Erguzel, Olgun (7 October 2020). "Up-conversion emission properties and unexpected white light emission from Er3+/Yb3+ doped Gd2O3 nanophosphors". Materials Research Express. 3 (10): 106201. doi:10.1088/2053-1591/3/10/106201. S2CID 138629139.
  14. ^ a b Zhu, Yongsheng; Xu, Wen; Li, Chongyang; Zhang, Hanzhuang; Dong, Biao; Xu, Lin; Xu, Sai; Song, Hongwei (2012-08-24). "Broad White Light and Infrared Emission Bands in YVO$_{4}$:Yb$^{3+}$,Ln$^{3+}$ (Ln$^{3+}$ = Er$^{3+}$, Tm$^{3+}$, or Ho$^{3+}$)". Applied Physics Express. 5 (9): 092701. doi:10.1143/APEX.5.092701. ISSN 1882-0778. S2CID 100620641.
  15. ^ a b c Stefanski, M.; Lukaszewicz, M.; Hreniak, D.; Strek, W. (2017-03-14). "Laser induced white emission generated by infrared excitation from Eu 3+ :Sr 2 CeO 4 nanocrystals". The Journal of Chemical Physics. 146 (10): 104705. Bibcode:2017JChPh.146j4705S. doi:10.1063/1.4978237. ISSN 0021-9606. PMID 28298121.
  16. ^ Strek, W.; Marciniak, L.; Gluchowski, P.; Hreniak, D. (September 2013). "Infrared laser stimulated broadband white emission of Yb3+:YAG nanoceramics". Optical Materials. 35 (11): 2013–2017. Bibcode:2013OptMa..35.2013S. doi:10.1016/j.optmat.2012.09.037.
  17. ^ Chaika, M.; Tomala, R.; Strek, W. (June 2021). "Laser induced broadband Vis and NIR emission from Yb:YAG nanopowders". Journal of Alloys and Compounds. 865: 158957. doi:10.1016/j.jallcom.2021.158957. ISSN 0925-8388. S2CID 234047841.
  18. ^ Bilir, Gökhan; Di Bartolo, B. (June 2014). "Production of bright, wideband white light from Y2O3 nano-powders induced by laser diode emission". Optical Materials. 36 (10): 1357–1360. Bibcode:2014OptMa..36.1357B. doi:10.1016/j.optmat.2014.03.027.
  19. ^ Bilir, Go¨khan; Liguori, Joseph (September 2014). "Laser diode induced white light emission of γ-Al2O3 nano-powders". Journal of Luminescence. 153: 350–355. Bibcode:2014JLum..153..350B. doi:10.1016/j.jlumin.2014.03.065.
  20. ^ Stefanski, M.; Głuchowski, P.; Strek, W. (December 2020). "Laser induced emission spectra of gallium nitride nanoceramics". Ceramics International. 46 (18): 29060–29066. doi:10.1016/j.ceramint.2020.08.077. S2CID 225201777.
  21. ^ Tomala, Robert; Hreniak, Dariusz; Strek, Wieslaw (November 2019). "Laser induced broadband white emission of Y2Si2O7 nanocrystals". Journal of Rare Earths. 37 (11): 1196–1199. doi:10.1016/j.jre.2019.03.014. S2CID 195417823.
  22. ^ a b Bilir, G.; Ozen, G.; Bettinelli, M.; Piccinelli, F.; Cesaria, M.; Di Bartolo, B. (August 2014). "Broadband Visible Light Emission From Nominally Undoped and $\hbox{Cr}^{3+}$ Doped Garnet Nanopowders". IEEE Photonics Journal. 6 (4): 1–11. doi:10.1109/JPHOT.2014.2337873. ISSN 1943-0655. S2CID 38757994.
  23. ^ a b Chen, Weibo; Shi, Yeqi; Chen, Zhi; Sang, Xiangwen; Zheng, Shuhong; Liu, Xiaofeng; Qiu, Jianrong (2015-09-03). "Near-Infrared Emission and Photon Energy Upconversion of Two-Dimensional Copper Silicates". The Journal of Physical Chemistry C. 119 (35): 20571–20577. doi:10.1021/acs.jpcc.5b04819. ISSN 1932-7447.
  24. ^ Chen, Xu; Xu, Wen; Zhu, Yongsheng; Zhou, Pingwei; Cui, Shaobo; Tao, Li; Xu, Lin; Song, Hongwei (2014). "Nd 2 O 3 /Au nanocomposites: upconversion broadband emission and enhancement under near-infrared light excitation". J. Mater. Chem. C. 2 (29): 5857–5863. doi:10.1039/C4TC00802B. ISSN 2050-7526.
  25. ^ Liu, Tong; Bai, Xue; Miao, Chuang; Dai, Qilin; Xu, Wen; Yu, Yanhao; Chen, Qidai; Song, Hongwei (2014-02-13). "Yb 2 O 3 /Au Upconversion Nanocomposites with Broad-Band Excitation for Solar Cells". The Journal of Physical Chemistry C. 118 (6): 3258–3265. doi:10.1021/jp408501k. ISSN 1932-7447.
  26. ^ a b Xu, Wen; Min, Xiaolei; Chen, Xu; Zhu, Yongsheng; Zhou, Pingwei; Cui, Shaobo; Xu, Sai; Tao, Li; Song, Hongwei (May 2015). "Ag-SiO2-Er2O3 Nanocomposites: Highly Effective Upconversion Luminescence at High Power Excitation and High Temperature". Scientific Reports. 4 (1): 5087. doi:10.1038/srep05087. ISSN 2045-2322. PMC 4035579. PMID 24867159.
  27. ^ a b Strek, Wieslaw; Cichy, Bartlomiej; Radosinski, Lukasz; Gluchowski, Pawel; Marciniak, Lukasz; Lukaszewicz, Mikolaj; Hreniak, Dariusz (January 2015). "Laser-induced white-light emission from graphene ceramics–opening a band gap in graphene". Light: Science & Applications. 4 (1): e237. Bibcode:2015LSA.....4E.237S. doi:10.1038/lsa.2015.10. ISSN 2047-7538.
  28. ^ a b Strek, Wieslaw; Tomala, Robert; Lukaszewicz, Mikolaj; Cichy, Bartlomiej; Gerasymchuk, Yuriy; Gluchowski, Pawel; Marciniak, Lukasz; Bednarkiewicz, Artur; Hreniak, Dariusz (March 2017). "Laser induced white lighting of graphene foam". Scientific Reports. 7 (1): 41281. Bibcode:2017NatSR...741281S. doi:10.1038/srep41281. ISSN 2045-2322. PMC 5256029. PMID 28112254.
  29. ^ Strek, Wieslaw; Tomala, Robert (February 2020). "Laser induced broadband emission spectra of graphene foam". Physica B: Condensed Matter. 579: 411840. Bibcode:2020PhyB..57911840S. doi:10.1016/j.physb.2019.411840. S2CID 209914184.
  30. ^ Strek, Wieslaw; Tomala, Robert; Olejniczak, Adam; Lukowiak, Anna; Ignatenko, Oleg; Cichy, Bartłomiej; Zhaludkevich, Aliaksandr; Konovalova, Alexandra (2018-05-17). "The bright white emission of µ-diamonds". In Taccheo, Stefano; Ferrari, Maurizio; Mackenzie, Jacob I. (eds.). Fiber Lasers and Glass Photonics: Materials through Applications. Strasbourg, France: SPIE. p. 6. doi:10.1117/12.2318052. ISBN 978-1-5106-1892-3. S2CID 139173970.
  31. ^ Dornsiepen, Eike; Dobener, Florian; Mengel, Nils; Lenchuk, Olena; Dues, Christof; Sanna, Simone; Mollenhauer, Doreen; Chatterjee, Sangam; Dehnen, Stefanie (June 2019). "White‐Light Generation Upon In‐Situ Amorphization of Single Crystals of [{(Me 3 P) 3 AuSn}(PhSn) 3 S 6 ] and [{(Et 3 P) 3 AgSn}(PhSn) 3 S 6 ]". Advanced Optical Materials. 7 (12): 1801793. doi:10.1002/adom.201801793. ISSN 2195-1071. S2CID 131854889.
  32. ^ Rosemann, N. W.; Eussner, J. P.; Beyer, A.; Koch, S. W.; Volz, K.; Dehnen, S.; Chatterjee, S. (2016-06-10). "A highly efficient directional molecular white-light emitter driven by a continuous-wave laser diode". Science. 352 (6291): 1301–1304. Bibcode:2016Sci...352.1301R. doi:10.1126/science.aaf6138. ISSN 0036-8075. PMID 27284190. S2CID 206648977.
  33. ^ Ye, Huanqing; Bogdanov, Viktor; Liu, Sheng; Vajandar, Saumitra; Osipowicz, Thomas; Hernández, Ignacio; Xiong, Qihua (2017-12-07). "Bright Photon Upconversion on Composite Organic Lanthanide Molecules through Localized Thermal Radiation". The Journal of Physical Chemistry Letters. 8 (23): 5695–5699. doi:10.1021/acs.jpclett.7b02513. hdl:10356/140364. ISSN 1948-7185. PMID 29099188.
  34. ^ a b c Ryabochkina, P. A.; Khrushchalina, S. A.; Yurlov, I. A.; Egorysheva, A. V.; Atanova, A. V.; Veselova, V. O.; Kyashkin, V. M. (2020). "Blackbody emission from CaF 2 and ZrO 2 nanosized dielectric particles doped with Er 3+ ions". RSC Advances. 10 (44): 26288–26297. Bibcode:2020RSCAd..1026288R. doi:10.1039/D0RA04776G. ISSN 2046-2069. PMC 9055429. PMID 35519758.
  35. ^ Zhu, Yongsheng; Cui, Shaobo; Liu, Mao; Liu, Xuyan; Lu, Cheng; Xu, Xiumei; Xu, Wen (2015-07-01). "Observation of upconversion white light and ultrabroad infrared emission in YbAG:Ln 3+ (Ln = Nd, Sm, Tb, Er)". Applied Physics Express. 8 (7): 072602. Bibcode:2015APExp...8g2602Z. doi:10.7567/APEX.8.072602. ISSN 1882-0778. S2CID 96670200.
  36. ^ Tomala, Robert; Strek, Wieslaw (October 2019). "Emission properties of Nd3+:Y2Si2O7 nanocrystals under high excitation power density". Optical Materials. 96: 109257. Bibcode:2019OptMa..9609257T. doi:10.1016/j.optmat.2019.109257. S2CID 202070772.
  37. ^ a b c d Strek, W.; Tomala, R.; Marciniak, L.; Lukaszewicz, M.; Cichy, B.; Stefanski, M.; Hreniak, D.; Kedziorski, A.; Krosnicki, M.; Seijo, L. (2016). "Broadband anti-Stokes white emission of Sr 2 CeO 4 nanocrystals induced by laser irradiation". Physical Chemistry Chemical Physics. 18 (40): 27921–27927. Bibcode:2016PCCP...1827921S. doi:10.1039/C6CP04904D. ISSN 1463-9076. PMID 27722306.
  38. ^ Cinkaya, Hatun; Eryurek, Gonul; Di Bartolo, Baldassare (March 2018). "White light emission based on both upconversion and thermal processes from Nd3+ doped yttrium silicate". Ceramics International. 44 (4): 3541–3547. doi:10.1016/j.ceramint.2017.11.042.
  39. ^ a b Wu, Jianhong; Xu, Cheng; Qiu, Jianrong; Liu, Xiaofeng (2018). "Conversion of constant-wave near-infrared laser to continuum white light by Yb-doped oxides". Journal of Materials Chemistry C. 6 (28): 7520–7526. doi:10.1039/C8TC01067F. ISSN 2050-7526.
  40. ^ a b c Stefanski, M.; Lukaszewicz, M.; Hreniak, D.; Strek, W. (December 2017). "Broadband laser induced white emission observed from Nd3+ doped Sr2CeO4 nanocrystals". Journal of Luminescence. 192: 243–249. Bibcode:2017JLum..192..243S. doi:10.1016/j.jlumin.2017.06.064.
  41. ^ Tabanli, S.; Yilmaz, H. Cinkaya; Bilir, G.; Erdem, M.; Eryurek, G.; Bartolo, B. Di; Collins, J. (2018). "Broadband, White Light Emission from Doped and Undoped Insulators". ECS Journal of Solid State Science and Technology. 7 (1): R3199–R3210. doi:10.1149/2.0261801jss. ISSN 2162-8769. S2CID 102891235.
  42. ^ Wang, Jiwei; Hao, Jian Hua; Tanner, Peter A. (August 2015). "Persistent luminescence upconversion for Er2O3 under 975nm excitation in vacuum". Journal of Luminescence. 164: 116–122. Bibcode:2015JLum..164..116W. doi:10.1016/j.jlumin.2015.03.018. hdl:10397/25191.
  43. ^ Marciniak, L.; Strek, W.; Hreniak, D.; Guyot, Y. (2014-10-27). "Temperature of broadband anti-Stokes white emission in LiYbP 4 O 12 : Er nanocrystals". Applied Physics Letters. 105 (17): 173113. Bibcode:2014ApPhL.105q3113M. doi:10.1063/1.4900965. ISSN 0003-6951.
  44. ^ Debasu, Mengistie L.; Ananias, Duarte; Pastoriza‐Santos, Isabel; Liz‐Marzán, Luis M.; Rocha, J.; Carlos, Luís D. (2013). "All-In-One Optical Heater-Thermometer Nanoplatform Operative From 300 to 2000 K Based on Er3+ Emission and Blackbody Radiation". Advanced Materials. 25 (35): 4868–4874. Bibcode:2013AdM....25.4868D. doi:10.1002/adma.201300892. ISSN 1521-4095. PMID 23696297. S2CID 7055304.
  45. ^ Tomala, Robert; Strek, Wieslaw (2019-10-01). "Emission properties of Nd3+:Y2Si2O7 nanocrystals under high excitation power density". Optical Materials. 96: 109257. Bibcode:2019OptMa..9609257T. doi:10.1016/j.optmat.2019.109257. ISSN 0925-3467. S2CID 202070772.
  46. ^ Verma, R.K.; Rai, Anita; Kumar, K.; Rai, S.B. (July 2010). "Up and down conversion fluorescence studies on combustion synthesized Yb3+/Yb2+: MO-Al2O3 (M=Ca, Sr and Ba) phosphors". Journal of Luminescence. 130 (7): 1248–1253. Bibcode:2010JLum..130.1248V. doi:10.1016/j.jlumin.2010.02.033.
  47. ^ Zhu, Siqi; Wang, Chunhao; Li, Zhen; Jiang, Wei; Wang, Yichuan; Yin, Hao; Wu, Lidan; Chen, Zhenqiang; Zhang, Ge (2016-05-15). "High-efficiency broadband anti-Stokes emission from Yb^3+-doped bulk crystals". Optics Letters. 41 (10): 2141–4. Bibcode:2016OptL...41.2141Z. doi:10.1364/OL.41.002141. ISSN 0146-9592. PMID 27176947. S2CID 32498982.
  48. ^ Stefanski, Mariusz; Tomala, Robert; Strek, Wieslaw (2020). "Studies of graphene influence on the laser induced white emission spectra of Sr 2 CeO 4 /graphene flake composites". Dalton Transactions. 49 (26): 9130–9136. doi:10.1039/D0DT01405B. ISSN 1477-9226. PMID 32578638. S2CID 220045636.
  49. ^ Miao, Chuang; Liu, Tong; Zhu, Yongsheng; Dai, Qilin; Xu, Wen; Xu, Lin; Xu, Sai; Zhao, Yi; Song, Hongwei (2013-09-01). "Super-intense white upconversion emission of Yb_2O_3 polycrystals and its application on luminescence converter of dye-sensitized solar cells". Optics Letters. 38 (17): 3340–3. Bibcode:2013OptL...38.3340M. doi:10.1364/OL.38.003340. ISSN 0146-9592. PMID 23988951.
  50. ^ Dornsiepen, Eike; Dobener, Florian; Chatterjee, Sangam; Dehnen, Stefanie (2019-11-18). "Controlling the White‐Light Generation of [(RSn) 4 E 6 ]: Effects of Substituent and Chalcogenide Variation". Angewandte Chemie International Edition. 58 (47): 17041–17046. doi:10.1002/anie.201909981. ISSN 1433-7851. PMC 6899930. PMID 31509340.
source: http://en.wikipedia.org/wiki/Draft:Laser_Induced_White_Emission