1. Introduction

Over the past two decades, 1-µm ytterbium-doped ultra-short cavity fiber laser, including single-frequency fiber laser (SFFL) and high-repetition-rate passively mode-locked fiber laser (MLFL), unlocking a plethora of applications across diverse industries such as scientific research, biomedical and national defense [1–8]. The longitudinal mode interval in SFFL and the pulse repetition rate in MLFL are inversely proportional to the length of the laser cavity, thus, an ultra-short cavity, centimeter or even millimeter scale, is required. Consequently, active fibers doping with high rare-earth (RE) concentration have become highly desirable to facilitate lasing within the shortened cavity length.

RE-doped phosphate glass fibers are commonly selected as the gain medium for ultra-short cavity lasers due to their resistance to concentration quenching and photo-darkening (PD) [9,10]. These properties make phosphate glass fibers an excellent choice for achieving stable and efficient single-frequency operation. No3 advancements in the field include a 400-mW single-frequency Yb³⁺ doped phosphate fiber laser reported by S. Xu et al. in 2011 [11] and an output power record of 1.15 W for phosphate YDF-based SFFL reported recently by S. Fu et al. in 2021 [12]. In the realm of high repetition rate MLFL, H. Chen et al. achieved a passively mode-locked YDFL with a fundamental repetition rate of 5 GHz in 2017 [13], and the highest fundamental repetition rate record of 12.5 GHz was demonstrated using a 7.6 mm phosphate YDF by W. Wang et al. in 2019 [14]. However, phosphate glass fibers do possess certain limitations, despite their remarkable properties. One notable limitation is their relatively low thermal and mechanical stability, impacting their long-term performance and reliability in practical applications. Additionally, the fusion process between phosphate glass fibers and commercial silica fibers presents challenges, limiting their seamless integration with existing fiber systems.

Utilization of composite fiber with a phosphate core and silica or silicate cladding is one potential solution to address the limitations of phosphate glass fiber [15–17]. However, the strong diffusion between core and cladding materials in such fibers often results in lower doping concentration compared to phosphate fibers and leads to inhomogeneities in the refractive index distribution, deteriorating the beam quality. The pump-to-signal conversion efficiency of the SFFLs fabricated on the Yb-doped composite fiber was only around 10% at an operation wavelength of 1030 nm [15]. Another promising approach involves composite fiber with a YAG-derived core and a silica fiber. Researchers have achieved all-fiberized SFFLs using YAG-derived gain fibers, demonstrating high slope efficiency and output power [18–20]. However, the diffusion problem must be addressed due to the molten core fabrication method employed for single-crystal-derived multicomponent glass fibers. Additionally, the high numerical aperture (NA) of YAG-derived fibers may lead to a modal mismatch when integrated with commercial silica fiber.

Silica-based fibers offer numerous advantages, making them the ideal choice for fiber laser systems. The silica fibers possess high strength, thermal robustness, and chemical inertness, allowing them to withstand harsh environmental conditions and ensuring long-term stability and reliability in practical application. Furthermore, their compatibility with commercial fiber devices enables seamless integration, enhancing the versatility and scalability of the laser system. Recently, a distributed Bragg reflector (DBR) SFFL utilizing a 1.2 cm-long commercial silica-based YDF achieved remarkable performance [21]. This SFFL achieved an impressive output power of 642 mW, setting a new record for both power and efficiency in SFFLs based on Yb³⁺ doped silica fiber. However, increasing the rare earth doping level in silica glass is not straightforward due to challenges such as ion clustering and phase separation. These phenomena can lead to cooperative up-conversion, resulting in energy loss through other transfer channels [22]. In the case of YDF, it produces more energetic photons and leads to the formation of color centers in the glass, contributing to PD [23]. The PD-related color centers increase background loss at the lasing wavelength, resulting in a degradation of laser performance over time.

To mitigate PD, co-dopants such as Al, P, and Ce are introduced in the core composition of the fiber. Al doping increases the solubility of rare earth ions and effectively suppresses PD [24]. On the other hand, the dissolution efficiency of P to Yb³⁺ clusters is higher than that of Al, resulting in more excellent resistance to the PD effect [25,26]. Nevertheless, it is important to note that the absorption and emission cross-sections of phosphosilicate fibers are approximately half the size of those in aluminosilicate fibers. Therefore, aluminophosphosilicate fiber strikes a balance between PD resistance and pump-to-signal conversion efficiency (PCE), making it a promising candidate for the development of 1 µm fiber lasers. Furthermore, P can combine with Al to form AlPO₄, decreasing the refractive index of optical fiber, and the increase of AlPO₄ joint concentration in Yb-doped silica glass can lead to a decrease in Yb cluster concentration [27]. Besides, Ce ions doping can effectively suppress the PD effect by trapping color center-related holes due to its dual ionic states: positive tetravalent (Ce⁴⁺) and trivalent (Ce³⁺) [28,29]. Therefore, Yb/Al/P/Ce co-doped silica fibers show promise in terms of high ytterbium concentration, high PD resistance, and excellent laser performance. However, limited studies have reported on high Yb³⁺ concentration Yb/Al/P/Ce co-doped silica fibers and their PD characteristics, laser performance and its application in ultrashort cavity fiber laser.

In this paper, we developed a Yb/Al/P/Ce co-doped silica-based fiber with 2.5 wt% Yb ions doping concentration using the MCVD combined with the solution doping method. The characteristics of the homemade heavily Yb³⁺ doped silica fiber were thoroughly investigated, demonstrating excellent performance for ultrashort cavity fiber laser applications. Furthermore, we propose a compact and robust SFFL with a linewidth of 14 kHz and a compact passively MLFL with a fundamental repetition rate of 1.23 GHz. These laser systems were extensively studied to showcase the superior performance of this homemade heavily Yb³⁺ doped silica fiber.

2. Fiber characteristics

The Yb/Al/P/Ce-co-doped silicate core preform was prepared by MCVD and conventional solution doping process. The procedure began with the deposition of a porous silica layer within a chemically polished silica tube (F300, Heraeus) using a SiCl₄ flow of 200 mL/min. To ensure uniform porosity, the oxy-hydrogen burner was set to a temperature of 1500°C. Following the deposition of pure silica soot, the soot was immersed in a Yb-containing solution and subjected to a subsequent drying step. For the co-doping of P₂O₅, a flow of POCl₃-O₂ gas mixture was introduced. Subsequent to this co-doping step, the porous soot tube underwent consolidation and collapsed into a transparent solid fiber preform. This consolidation process involved heating the tube to a temperature of 2200°C using a moving burner. Finally, the preform was drawn into a fiber under optimized conditions to ensure high mechanical strength. The radial refractive index profile (RIP) of the fiber, as measured by an optical fiber analyzer (IFA-100), is presented in Fig. 1 (a). The refractive index difference between the Yb-doped fiber core and the pure silica cladding is approximately 0.005, corresponding to an effective numerical aperture (NA) of around 0.12. The cladding diameter is 125 µm, while the core diameter of YAPCS fiber is 6 µm. This configuration is compatible with commercially available 1.0 µm single-mode fiber. It is worth noting that there is a central dip at the core region of the RIP, resulting from the natural evaporation of P₂O₅ during the high temperature collapsing process. This leads to a refractive index fluctuation of approximately 1.2 × 10⁻³. However, it is believed that this fluctuation will not significantly affect the single-mode operation and will not cause a noticeable mode mismatch.

 

Fig. 1. (a) Refractive index profile of the YDF. (b) Radial concentration profile of the YDF core. (c) core attenuation and (d) absorption spectrum of the YDF

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To accurately determine the concentrations of Yb, Al, P, and Ce in the fiber preform sample, an inductively coupled plasma optical emission spectrometer (ICP-OES) was utilized. The measured absolute concentrations of Yb, Al, P, and Ce in the fabricated preform were found to be 25000, 18000, 37500, and 3000 ppm-wt, respectively. The high concentration of Yb in this Yb-doped silica fiber is crucial for achieving the desired laser performance and efficiency. To further investigate the elemental distribution, the distributions of Yb₂O₃, Al₂O₃, P₂O₅, and Ce₂O₃ in the cross-section of the YDF were obtained using an electron probe micro analyzer (EPMA, JEOL, JXA-8230) and are depicted in Fig. 1(b). It can be observed that there are noticeable central dips in the distributions of Yb and Al, which align with the RIPs. This correlation confirms the consistency between the refractive index and the dopant concentration profiles. The core background attenuation spectrum was determined using the cut-back method with a white light source, as illustrated in Fig. 1(c). The measured background attenuation remains below 20 dB/km within the wavelength range of 1200 to 1600 nm. Additionally, an OH^- absorption peak is observed, with an attenuation of approximately 15 dB/km. These results indicate an excellent control over the loss during the fiber fabrication process, ensuring low overall attenuation and favorable signal transmission characteristics. Furthermore, the core absorption spectrum of Yb³⁺ in the fiber was also measured and is presented in Fig. 1(d). The pump absorption coefficients of the YDF were found to be approximately 1400 dB/m at 976 nm and 340 dB/m at 920 nm. These absorption coefficients indicate the efficiency of Yb³⁺ absorption at these pump wavelengths, which are crucial for achieving effective lasing in a short-length YDF laser cavity.

To evaluate the gain performance and the pump-to-signal conversion efficiency of the YAPCS fiber, an all-fiber amplifier was constructed, as shown in Fig. 2(a). A SFFL operating at 1064 nm was utilized as a seed laser. The YAPCS fiber was fusion-spliced with two 980/1064 nm wavelength-division multiplexers (WDM). To suppress Fresnel reflection, the amplified signal output port of the second WDM was fusion-spliced with an angled physical contact (APC) patch cord. For gain performance measurement, the input power of the seed laser was attenuated to -30 dBm to ensure accurate measurement of the small-signal gain, and the lengths of YAPCS fiber were chosen to be 20, 30, and 40 mm. An optical spectrum analyzer (OSA, Yokogawa AQ6370D) was employed to measure the amplified signal power and calculate the gain coefficient. Figure 2(b) illustrates the relationship between the net gain and the pump power for various fiber lengths. Notably, when the active fiber length was 40 mm and the pump power was 100 mW, the gain of the YAPCS fibers reached 4.0 dB. Across all tested fiber lengths, the measured gain coefficient of all fiber lengths was approximately 1.0 dB/cm, indicating a consistent gain performance. For the PCE experiment, to achieve saturated amplification, the signal power was set at 50 mW. The length of YAPCS fiber was optimal to about 15 cm to attain sufficient absorption of pump light and achieve maximum efficiency. As is shown in Fig. 2(c), the signal was amplified to 175 mW under a pump power of 256 mW, and the corresponding PCE was ∼61%. These results demonstrate the capabilities of the YAPCS fiber to provide sufficient gain for efficient lasing or amplification in short-length fiber laser systems.

 

Fig. 2. (a) The schematic diagram of the all-fiber amplifier experimental setup. (b) Measured gain properties and (c) pump-to-signal conversion efficiency of the heavily Yb³⁺-doped silica fiber

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PD-induced excess loss measurement is crucial for assessing the PD performance and clustering properties of YDF, providing valuable insights into their practical applicability. In our study, we conducted PD-induced excess loss testing on the developed highly Yb³⁺-doped silica fiber, utilizing a 915 nm core pumping scheme. The pump power was consistently set at 250 mW, and the fiber length chosen for the measurement was carefully selected to ensure a comparable degree of inversion. The PD performance of the Yb/Al/P/Ce fiber is shown in Fig. 3 in comparison to a Yb/Al/P co-doped fiber, with Yb, Al, and P concentrations of 20000, 17000, and 31000 ppm-wt, respectively. Interestingly, despite the lower doping concentration, the Yb/Al/P fiber demonstrated a higher level of PD-induced loss. Specifically, through the application of the standard stretched exponential function fitting [30], we calculated the PD-induced equilibrium excess losses α_eq of the Yb/Al/P/Ce co-doped fiber at 633 nm to be 52 dB/m. In contrast, for the Yb/Al/P co-doped fiber, the PD-induced equilibrium excess loss at 633 nm was calculated to be 117 dB/m, indicating a 2.25-fold higher value compared to the Yb/Al/P/Ce co-doped fiber. The results could be attributed to the introduction of Ce and the higher P concentration. These factors reduce PD-induced loss in highly Yb³⁺ doped silica fibers, consequently enhancing overall performance and longevity in practical applications.

 

Fig. 3. Photodarkening of Yb/Al/P/Ce co-doped and Yb/Al/P co-doped fiber

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3. Single frequency DBR fiber laser

The experimental setup of the single-frequency DBR fiber laser is shown in Fig. 4(a). A 976 nm LD with a maximum output power of approximately 460 mW was utilized as the pump source. The pump light was coupled into the heavily Yb-doped fiber using a 980/1064 nm wavelength division multiplexer (WDM). The DBR ultrashort cavity consists of a polarization-maintaining low-reflectivity FBG (PM-LR-FBG), a segment of the heavily YDF, and a high-reflectivity FBG (HR-FBG). The reflectivity of the slow axis of the PM-LR-FBG and the HR-FBG were 80.4% and 99.9%, respectively, with corresponding 3-dB bandwidths of 0.04 nm and 0.18 nm. In this setup, the physical length of the PM-LR-FBG and HR-FBG were 2.0 cm and 1.0 cm, respectively. The effective lengths of the two FBGs in the laser cavity were approximately 0.62 cm and 0.12 cm [31]. The 3-dB bandwidth of the PM-LR-FBG, which corresponds to approximately 10.6 GHz, indicates that the longitudinal mode spacing should be larger than 5.3 GHz. Therefore, a gain fiber length of 10 mm was chosen to achieve a longitudinal mode spacing of approximately 5.9 GHz, ensuring an effective single-longitudinal-mode operation. To prevent instability, such as longitudinal mode fluctuations or self-pulsing caused by reverse light entering the laser cavity, a slow-axis-working PM isolation (PM-ISO) with an isolation of about 28 dB is incorporated into the setup. For efficient heat dissipation, the laser cavity was positioned on a copper heat sink and embedded in thermal conductive glue. To maintain a stable SLM operation, a temperature controller (TEC) was employed. The TEC regulates and maintains a constant temperature at 25°C within the laser cavity, ensuring consistent performance and minimizing temperature-induced fluctuations.

 

Fig. 4. The schematic diagram of the SFFL experimental setup. (b) Output power as a function of pump power of the SFFL. Inset shows the long-term stability of the SFFL. (c) The optical spectrum of the SFFL measured with 0.2 nm. The inset shows the laser spectrum measured with 0.02 nm resolution in a span of 1 nm

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The output power of the SFFL was measured with a power meter (Thorlabs, S145C), and the results are presented in Fig. 4(b). The laser exhibited a pump threshold of 10.5 mW, indicating the low cavity losses and high gain provided by the heavily Yb³⁺-doped silica fiber. The maximum achieved output power was 75 mW, obtained with the maximum available pump power of 460 mW, and the slope efficiency was approximately 16.4%. The measured output power and efficiency surpass the results reported using a silica-based YDF with an absorption coefficient of 1700dB/m at 976 nm [32]. The inset of Fig. 4(b) depicts the stability of the output power at 70 mW over a period of 120 minutes. No significant power degradation was observed, and the fluctuation in output power was calculated to be 0.52% (rms), highlighting the excellent stability of the SFFL. Due to using a PM-LR FBG as the output coupler, the laser operated in a single linear polarization mode. The polarization extinction ratio was measured to be greater than 20 dB across all the pump power levels, indicating a high level of polarization purity. The typical optical spectrum of the SFFL was measured using an OSA, and the results are displayed in Fig. 4(c). The spectrum clearly indicates the central wavelength of the laser at 1064 nm, and an optical signal-to-noise ratio (OSNR) of the laser exceeds 75 dB, which approaches the close-in dynamic range of the OSA, indicating a high level of optical spectrum purity. The inset of Fig. 4(c) provides a closer view of the laser spectrum within a narrow wavelength range of 1 nm, with a measurement resolution of 0.02 nm. The highly symmetric profile is a characteristic feature of a single-frequency laser.

To further investigate the longitudinal mode behavior of the output laser, a scanning Fabry-Perot interferometer (FPI, Thorlabs, SA200-8B) and an oscilloscope (Agilent Inc., DSO5052A) were utilized. The free spectral range (FSR) and fitness of the FPI were 1.5 GHz and 200, respectively, offering a resolution of 7.5 MHz. Figure 5(a) depicts the voltage ramp applied to the piezoelectric transducer (PZT) and the scanning FPI signal of the output laser at maximum output power, as measured by the oscilloscope. Notably, no additional side mode peaks were observed between the two major transmission peaks, indicating that the output laser operated in a SLM operation. The linewidth of the DBR fiber laser was evaluated using a delayed self-heterodyne method based on a Mach-Zehnder interferometer. This setup includes a 20 km single-mode fiber delay line and a 150 MHz acoustic optical modulator, providing a resolution of about 7.5 kHz. Figure 5(b) illustrates the 150 MHz beat frequency signal within a range of 4 MHz measured by a frequency spectrum analyzer (Keysight, N9020B) with a resolution bandwidth (RBW) of 100 Hz. To mitigate the impact of 1/f noise, the laser linewidth is typically calculated using 1/20 of the 20 dB bandwidth of the beat frequency signal. By fitting a Lorentzian curve to the measured data in the inset of Fig. 5(b), the 20 dB linewidth of the beat frequency signal is determined to be 280 kHz, indicating the DBR laser linewidth is approximately 14 kHz.

 

Fig. 5. (a) Longitudinal mode characteristics of the SFFL measured by the scanning FPI. (b) Measured self-heterodyne signal of the SFFL with the Lorentzian fitted linewidth

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To achieve precise wavelength tuning around 1064 nm, the temperature of the FBG was meticulously regulated using a TEC with an accuracy of 0.01 °C. Figure 6(a) illustrates the wavelength tuning capabilities, showcasing a tuning range of over 340 pm when the TEC temperature increased from 10 °C to 50 °C. The laser wavelength exhibited a linear relationship with the temperature, with a coefficient of 6.74 pm/°C. To validate the wavelength tuning process, a wavelength meter (High Finesse, WS7) with a resolution of 60 MHz was employed. At the pump power of 300 mW, the wavelength-temperature cycle curve was measured and depicted in Fig. 6(b). Notably, the curve exhibited a smooth variation without any sudden changes or discontinuities. This observation indicates the absence of mode hopping throughout the entire wavelength thermal tunning process, ensuring the robust SLM operation of the SFFL.

 

Fig. 6. (a) Laser wavelength versus different TEC temperatures. Inset: Output spectrum of the SFFL when temperature increases from 10 to 60 °C. (b) Wavelength-temperature cycle curve measured by a wavelength meter

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Table 1. Performance Comparison of DBR SFFLs based on silica YDF

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Fig. 7. (a) Experimental setup of the passively MLFL. (b) The output power of the MLFL as a function of pump power. (c) Optical spectrum of the MLFL. (d) Typical pulse train in a time span of 12 ns. (e) Radiofrequency (RF) spectrum of the mode-locked pulses. (f) The RF spectrum from 0 to 26.5 GHz. (g) Autocorrelation trace of the mode-locked pulses.

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Table 1 illustrates a comparison of ultra-short linear-cavity SFFLs based on various silica-based Yb³⁺-doped fibers. Sun et al. presented a single-frequency DBR laser operating at 1030 nm, employing a 1.1 cm long commercial Yb-doped silica fiber (Fibercore, DF1100). Their laser demonstrated a maximum output power exceeding 160 mW and a slope efficiency of 27% while maintaining a linewidth of 6 kHz. Sun et al. further demonstrated an ultrashort-cavity DBR laser operating at 1064 nm using the same gain fiber and length. In this case, the maximum output power was restricted to 13 mW with a slope efficiency of 3.4%. This relatively lower power output can be attributed to the fact that the emission cross-section at 1064 nm is inferior to that at 1030 nm, thereby limiting the achievable gain with the same active fiber length. Recently, Li et al. achieved an SFFL with an output power of 642 mW using a 1.2-cm-long commercial Yb³⁺-doped silica fiber (Coractive, YB406) with an absorption coefficient of 2400 dB/m at 976 nm. Notably, this represented the highest single-frequency laser power and efficiency reported using a DBR all-silica fiber laser. Generally, YDFs with higher doping concentrations and larger absorption coefficients exhibit enhanced gain coefficients. Nonetheless, concentration quenching can play a pivotal role in maintaining efficient pump conversion. For instance, it is important to note that, despite the higher absorption coefficients of the fibers used in Ref. 33 and 34 in comparison to our study, the attained power and efficiency were markedly lower than the results presented in this paper. In conclusion, it becomes exceptionally crucial to optimize the core glass composition to simultaneously increase the concentrations of rare-earth ions, mitigate the concentration quenching phenomenon, and maintain quantum conversion efficiency.

4. High-repetition-rate passively MLFL

To explore the potential of generating ∼1.0 µm ML fiber lasers with a high fundamental repetition rate, we conducted further investigations by using an all-fiber passively mode-locked laser cavity. The experimental setup is shown in Fig. 7(a). This cavity comprised a semiconductor saturable absorber mirror (SESAM) with a modulation depth of 8% and recovery time of 1 ps, a fiber-type dielectric film (DF) made of SiO₂/Ta₂O₅, and an 8.4 cm long Yb³⁺-doped silica fiber. The YDF was securely held in place with epoxy within a ceramic ferrule with an inner diameter of 125 µm. Both end facets of the fiber assembly were meticulously polished flat. The fiber-type DF was butt-coupled to one end facet of the YDF, and the pigtail of the DF was spliced to the common port of the 976/1064 nm WDM. The SESAM was connected to the other end facet of the YDF. The 976 nm pump laser was coupled to the system by fused splicing with the pump port of 976/1064 nm WDM. During the experimental measurements, the output power was detected using a power meter (Thorlabs, S145C), while the optical spectrum was measured by an OSA (Yokogawa AQ6370D). The temporal waveform of the laser pulses was recorded using an 8-GHz bandwidth digital oscilloscope (Keysight DSOV084A), and the radiofrequency (RF) spectrum was detected using a signal analyzer (Keysight N9020A). To determine the pulse duration, an autocorrelator (APE pulseCheck USB 150) was employed.

Figure 7(b) presents the relationship between the average output power and the launched pump power. The self-started continuous wave (CW) mode-locking of the oscillator is achieved when the pump power exceeds 84 mW. The output power shows a linear increase with pump power, with a slight improvement upon entering the CW mode-locking regime. The slope efficiency is approximately 32.4% for this laser system. The optical spectrum of the output pulses spans from 1062 to 1070 nm, with a peak wavelength at 1066.3 nm (Fig. 7(c)). The 3-dB spectral bandwidth is 3.7 nm, corresponding to a transform-limited pulse width of 323 fs, assuming a sech²-pulse shape. Figure 7(d) displays the mode-locked pulse train over a time span of 12 ns. Due to the high net gain of the heavily Yb³⁺- doped silica fiber, the mode-locked pulses exhibit a period of 812.5 ps within a laser cavity of centimeter-scale length, corresponding to a fundamental repetition rate of 1.23 GHz. The repetition rate is further confirmed in Fig. 7(e), where the fundamental frequency is observed at 1.23 GHz, consistent with the pulse train period. The repetition rate conforms to the cavity length, indicating the pulses are fundamentally mode-locked. The sidebands observed on both sides of the fundamental frequency result from the weak modulation caused by the polarization rotation during the vectorial operation of the mode-locked pulse train [35,36]. The RF spectrum exhibits an SNR of approximately 52 dB, and the side-mode suppression ratio (SMSR) is approximately 30 dB. Figure 7(f) gives the broadband RF spectrum from 0 to 26.5 GHz, revealing the stable CW mode-locking operation of our laser. The autocorrelation trace of the oscillators, shown in Fig. 7(g), exhibits a full width at half maximum (FWHM) of 9.9 ps. Assuming a sech²-pulse shape and accounting for the additional stretching factor of 1.54 due to convolution, the pulse duration is determined to be 6.4 ps, indicating the output pulses are chirped. These results confirm that this self-developed Yb³⁺-doped silica fiber is a promising gain medium for generating 1.0-µm ultrashort pulses with a high repetition rate.

5. Conclusion

In conclusion, we designed and fabricated a heavily Yb³⁺-doped silica-based fiber with a Yb/Al/P/Ce core glass composition, aiming to achieve high PD resistance. The core and cladding diameter are 6/125 µm, ensuring a single-mode operation for both the signal and pump wavelength with an NA of 0.12. The Yb concentration in the core glass was measured to be 25000 ppm, and the corresponding core absorption coefficient and gain coefficient are 1400 dB/m at 976 nm and 1.0 dB/cm at 1064 nm, respectively, providing an efficient gain property within a short-length laser cavity. The PD-induced equilibrium excess loss of this Yb/Al/P/Ce co-doped silica fiber was measured to be 52 dB/m, which is 2.25 times lower than that of the Yb/Al/P co-doped fiber, highlighting the significance of Ce doping in mitigating PD effects. Based on the self-developed Yb³⁺-doped silica fiber, we achieved efficient SFFL at a wavelength of 1064 nm with an OSNR exceeding 75 dB and a linewidth of 14 kHz. The maximum output power reached 75 mW, limited by the pump power, while maintaining a slope efficiency of 16.4%. Long-term output power stability analysis revealed an RMS fluctuation of 0.52%, indicating a high level of stability in this all-fiberized laser cavity. Furthermore, we demonstrated the generation of passively ML pulses at 1064 nm with a fundamental repetition rate of 1.23 GHz using an ultrashort cavity employing an 8.4-cm-long YDF. The pulse duration was measured to be 6.4 ps. These results confirm the effectiveness of the heavily Yb³⁺-doped silica fiber as an effective gain medium for generating narrow linewidth single-frequency lasers and high repetition rate pulse lasers in an ultrashort cavity at 1.0 µm. Overall, this study highlights the advantages of utilizing an all-fiber structure based on silica-based fiber, offering inherent benefits such as high stability and reliability, further enhancing the practicality and applicability of the developed fiber laser system.