Femtosecond Tm–Ho co-doped fiber laser using a bulk-structured Bi2Se3 topological insulator<xref rid="cpb_27_9_094219fn1" ref-type="fn">*</xref><fn id="cpb_27_9_094219fn1"><label>*</label>Project supported by the National Research Foundation of Korea (NRF) Grant Funded by the Korea Government (MSIT), Republic of Korea (Grant No. NRF-2018R1A2B6001641), Ministry of Science and ICT (MSIT) under the Information Technology Research Center (ITRC) Support Program (Grant No. IITP-2018-2015-0-00385), and supervised by the Institute for Information and Communications Technology Promotion (IITP).</fn>

Femtosecond Tm–Ho co-doped fiber laser using a bulk-structured Bi₂Se₃ topological insulator**

Project supported by the National Research Foundation of Korea (NRF) Grant Funded by the Korea Government (MSIT), Republic of Korea (Grant No. NRF-2018R1A2B6001641), Ministry of Science and ICT (MSIT) under the Information Technology Research Center (ITRC) Support Program (Grant No. IITP-2018-2015-0-00385), and supervised by the Institute for Information and Communications Technology Promotion (IITP).

Lee Jinho, Lee Ju Han^†

Measured XPS spectra of (a) Bi 4f region and (b) Se 3d region.