# Wavelength-Switchable Ytterbium-Doped Fiber Laser Based on All-Fiber Lyot Interferometer Filter  
[PERSON]  
1 The State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China; [EMAIL_ADDRESS] (Y.W. ); [EMAIL_ADDRESS] (Q.L. )1  
[PERSON]  
1 The State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China; [EMAIL_ADDRESS] (Y.W. ); [EMAIL_ADDRESS] (Q.L)1  
[PERSON]  
1 The State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China; [EMAIL_ADDRESS] (Y.W. ); [EMAIL_ADDRESS] (Q.L)1  
[PERSON]  
1 The State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China; [EMAIL_ADDRESS] (Y.W. ); [EMAIL_ADDRESS] (Q.L)1  
Footnote 1: [[https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci)]([https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci))  
Footnote 2: [[https://www.mdpi.com/journals/pdf/12](https://www.mdpi.com/journals/pdf/12)]([https://www.mdpi.com/journals/pdf/12](https://www.mdpi.com/journals/pdf/12))  
on wavelength-tunable YDFLs is one of the hot directions in the development of laser technology. Many researchers have carried out research on the realization of wavelength-tunable YDFLs. [PERSON] et al. reported a widely tunable ytterbium-doped single-frequency all-fiber laser based on a tunable filter and a comb filter manufactured by fusing a polarization-maintaining fiber (PMF) in a double-circulator interferometer to generate a hybrid filter; the single-wavelength-tunable operation was about 55 nm, with a 0.38 dB power fluctuation [9]. [PERSON] et al. designed a multifunctional acousto-optic tunable filter-based wavelength-tunable YDFL; its maximal wavelength tuning range and minimal resolved wavelength spacing were 80 and 1.5 nm, respectively [10]. [PERSON] et al. reported a wavelength-tunable YDFL using a Sagnac interferometer with a polarization-maintaining photonic crystal fiber, and 1034.276 to 1038.314 nm single-wavelength laser tuning and a 3.2 nm dual-wavelength tuning range were realized; the maximum wavelength power shift was 0.64 dB [11]. [PERSON] et al. designed a wavelength-tunable YDFL using a nonlinear amplifying loop mirror to generate a laser with a tuning range of 54 nm from 1011.8 nm to 1065.6 nm [12]. [PERSON] et al. presented a switchable YDFL based on a symmetrical long-period fiber grating fabricated by combining the cladding shaping with the thermal core expansion techniques using a CO\({}_{2}\)-laser glass-processing system. The experimental results showed a 49 dB signal-to-noise ratio (SNR) within the range from 1038 to 1080 nm [13]. [PERSON] et al. reported a wavelength-tunable YDFL based on a nonlinear amplifier loop mirror using a large-mode-area polarization-maintaining double-cladding fiber to realize 1034 to 1104 nm laser generation [14]. [PERSON] et al. presented a tunable dual-wavelength erbium-ytterbium-doped fiber laser based on a cascaded tunable band-pass filter and fiber Bragg grating, and the fiber laser-generated dual-wavelength emissions that varied from 3 nm to 10 nm [15]. [PERSON] et al. reported a dual-wavelength-tunable Er/Yb double-clad fiber laser through simple adjustments of a wave retarder, and the wavelength spacing could be tuned from 0.96 to 9 nm [16]. [PERSON] et al. presented a wavelength-tunable single-frequency YDFL based on a double-circulator interferometer, and the central wavelength of the laser beam could be tuned from 1040 nm to 1080 nm [17]. [PERSON] et al. reported a single- and dual-wavelength YDFL based on a Sagnac loop comb filter for the proposed fiber laser, and tuning ranges of 17.9 nm for the single-wavelength lasing output and 8.4 nm for the dual-wavelength lasing output were achieved [18]. [PERSON] et al. reported a broadband wavelength-tunable ring-cavity YDFL based on a fiber optical tunable filter that achieved a wide-band tunability from 1030 to 1090 nm [19]. [PERSON] et al.