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Chinese Optics Letters
Vol. 19, Issue 8, 081405 (2021)

Recent development of saturable absorbers for ultrafast lasers [Invited] | Editors' Pick

Mengyu Zhang, Hao Chen, Jinde Yin, Jintao Wang, Jinzhang Wang, and Peiguang Yan^*

Author Affiliations

Shenzhen Key Laboratory of Laser Engineering, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China

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DOI: 10.3788/COL202119.081405 Cite this Article Set citation alerts

Mengyu Zhang, Hao Chen, Jinde Yin, Jintao Wang, Jinzhang Wang, Peiguang Yan. Recent development of saturable absorbers for ultrafast lasers [Invited][J]. Chinese Optics Letters, 2021, 19(8): 081405 Copy Citation Text

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Fig. 1. SESAM-based mode-locked Yb:YAG TDL. (a) Schematic of the cavity design. (b) Beam profile at 350 W output power in CW operation. (c) Beam profile at 350 W in mode-locked operation. The vertical and lateral cuts of the beam are depicted as red lines with Gaussian fits. (d) Optical spectrum with the central wavelength of 1030 nm. (e) Autocorrelation (AC) trace. (f) Radio frequency (RF) spectrum with 42 dB signal-to-noise ratio. (a)–(f) Reproduced with permission^[85]. Copyright 2019, Optical Society of America.

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Fig. 2. Quantum dots (QDs) as active media for ultrafast mode-locked VECSEL. (a) V-shaped cavity designed with the SESAM and output coupler as end mirrors and the VECSEL gain chip as the folding mirror. (b) Epitaxial structure of the QD VECSEL and the standing wave intensity profile at the central wavelength of 1035 nm. (c) and (d) SESAM mode-locked VECSEL results with different cavity designs. (c) Pulse characterizations are measured with a pulse duration of 216 fs and a full width at half-maximum (FWHM) of 5.7 nm at 2.77 GHz repetition rate. (d) Pulses of 193 fs with 6.6 nm FWHM bandwidth and 1.67 GHz repetition rate. Reproduced with permission^[89]. Copyright 2018, IEEE.

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Fig. 3. Optically pumped high-power MIXSEL. (a) MIXSEL concept and SEM image: the MIXSEL semiconductor consists of two highly distributed Bragg reflectors (DBRs), a QD saturable absorption layer, a quantum well (QW) gain section, and an anti-reflective (AR) coating. (b) Photograph and sketch of the MIXSEL cavity: the sample straight cavity is formed by a MIXSEL chip and an output coupler. (c) RF spectrum, (d) optical spectrum, (e) AC trace intensity, and (f) beam quality measurement. (a)–(f) Reproduced with permission^[96]. Copyright 2010, Optical Society of America.

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Fig. 4. XUV light source generation based on HHG inside a mode-locked TDL. (a) Illustration of the experimental setup. (b) AC trace and (c) RF spectrum without a high-pressure xenon gas jet. (d) AC trace and (e) RF spectrum with high-pressure xenon gas jet. (f) Optical spectrum of the generated XUV light. (g) Amplitude and phase noise measurements of the mode-locked TDL with and without gas. (a)–(g) Reproduced with permission^[98]. Copyright 2017, Optical Society of America.

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Fig. 5. SESAM mode-locked

Tm, Ho : {CaYAlO}_{4}

laser. (a) Schematic of the mode-locked

Tm, Ho : {CaYAlO}_{4}

laser cavity. (b) AC trace of the mode-locked

Tm, Ho : {CaYAlO}_{4}

laser and (c) the corresponding optical spectra. (a)–(c) Reproduced with permission^[103]. Copyright 2018, Optical Society of America.

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Fig. 6. (a) Schematic of the mode-locked VECSEL cavity. OC, optical coupler mirror; HR, highly reflective folding mirror; GSAM, graphene SAM. (b) Picture of the GSAM by transferring single-layer graphene on an 8/λ

{SiO}_{2}

. (c) AC trace and (d) RF spectrum centered at the repetition rate of 2.5 GHz with 1 kHz resolution. (e) Tunable optical wavelength (from 935 to 981 nm) and average output powers with different gain chips. (a)–(e) Reproduced with permission^[136]. Copyright 2013, Optical Society of America.

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Fig. 7. SWCNT-PVA mode-locked fiber laser with stretched pulse generation. (a) Schematic of the laser setup and the dispersion distribution in the laser cavity. Normal dispersion is provided by the Er-doped fiber (EDF) and anomalous dispersion is provided by the Flexcore 1060 and SMF-28 fibers. WDM, wavelength division multiplexer; SMF, single-mode fiber; ISO, isolator; PC, polarization controller. (b) The nonlinear transmittance of SWCNT-PVA, which gives the modulation depth of 17%. (c) Optical spectrum with the bandwidth of 63 nm. (d) AC trace with a Gaussian fit. (a)–(d) Reproduced with permission^[145]. Copyright 2019, American Institute of Physics.

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Fig. 8.

{HfS}_{2}

-microfiber SA for mode-locked fiber lasers. (a) Schematic diagram of PCF-assisted

{HfS}_{2}

deposition system. (b) Picture of the deposition process. Inset displays the end-face of the PCF. Optical microscope images of the

{HfS}_{2}

-microfiber SA (c) before and (d) after launching a 630 nm laser. (e)–(h) Optical characterizations of the laser results. (e) Optical spectrum; (f) optical spectra of soliton operation for 4 h; (g) AC trace; (h) RF spectrum. (a)–(h) Reproduced with permission^[155]. Copyright 2018, Wiley-VCH.

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Fig. 9. Ultrafast laser mode-locking with double-covered

{ReS}_{2}

-microfiber (DCRM). (a) Schematic of the

{ReS}_{2}

film preparation by the vacuum filtration method, which includes sonication, centrifugation, and filtration with different

{ReS}_{2}

suspension volumes (10 mL, 20 mL, 30 mL, and 40 mL). (b) Schematic of the DCRM where the microfiber is sandwiched between two

{ReS}_{2}

nanosheet films. The

{SiO}_{2}

substrate is coated by a

{MgF}_{2}

layer. (c) Nonlinear transmittance of the DCRM at 1550 nm. (d)–(f) Typical laser characteristics. (d) Optical spectrum, (e) oscilloscope trace, and (f) AC trace. (a)–(f) Reproduced with permission^[157]. Copyright 2018, IEEE.

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Fig. 10. Ultrafast mode-locked laser using inkjet-printed BP SA. (a) Photograph of formulated BP ink. (b) Droplet drying process without (left) and with (right) introducing recirculated Marangoni flow. (c) Optical photographs (left) and atomic force microscope (AFM) images (right) of the dried droplets. (d) Dark field optical micrographs of the printed tracks on

Si / {SiO}_{2}

, glass, and PET. (e) Printed BP-SA sandwiched between two fiber patch cords. (f) Optical spectra of soliton mode-locking across 30 days. Superposition of the (g) optical spectrum and (h) RF spectrum at the fundamental frequency of 31.6 MHz after 0, 174, 534, and 714 h of operation. (a)–(h) Reproduced with permission^[161]. Copyright 2017, Nature.

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Fig. 11. Ultrafast mode-locking with inkjet-printed

{2 H - MoS}_{2}

optical devices. (a) Schematic picture of the EDFL cavity. (b) AC trace fitted with a Gaussian curve. (c) Output laser spectrum and (d) RF spectrum at a fundamental frequency of 20.176 MHz. (e) Measured fundamental frequency (top), central wavelength (medium), and FWHM bandwidth (down) generated from 16 individual

{2 H - MoS}_{2}

SAs. (a)–(e) Reproduced with permission^[158]. Copyright 2020, American Association for the Advancement of Science.

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Fig. 12. High-energy soliton pulse generation by magnetron sputtering deposition (MSD) grown

{MoTe}_{2}

-microfiber SA. (a) SEM image of the microfiber coated with

{MoTe}_{2}

film and (b) cross-section view of the

{MoTe}_{2}

-microfiber. Microscope image of the

{MoTe}_{2}

-microfiber (c) without and (d) with guiding a red light. (e) Nonlinear transmittance properties of

{MoTe}_{2}

SA at 1.5 µm and 2 µm. AC traces at (f) 1.5 µm and (g) 2 µm, respectively. (a)–(g) Reproduced with permission^[196]. Copyright 2018, Chinese Laser Press.

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Fig. 13. Self-starting mode-locking by fiber-integrated

{WS}_{2}

-SAM. (a) Schematic picture of mode-locked fiber laser cavity. (b)–(e) Mode-locked laser performances. (b) Oscilloscope trace; (c) RF spectrum with a fundamental frequency of 396 MHz; (d) laser spectra using different fiber Bragg gratings (FBGs); (e) laser slope efficiencies under different operating wavelengths. (a)–(e) Reproduced with permission^[198]. Copyright 2015, IEEE.

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Fig. 14.

{WS}_{2} - {MoS}_{2} - {WS}_{2}

heterostructure SAM for mode-locked fiber lasers. (a) Schematic image of the fiber-integrated heterostructure SA. (b) SEM image of the measured lateral thickness (48.4/20.7/62.8 nm) on a silicon wafer. (c) The predicted band structure of

{MoS}_{2} - {WS}_{2}

heterostructure with a type II heterojunction. CB is the conduction band, and VB is the valence band. (d) Nonlinear optical absorption of the heterostructure SA. (e) Illustration of a typical EDFL cavity. (f) Output laser spectrum. (g) AC trace of the output pulse. (h) RF spectrum. (a)–(h) Reproduced with permission^[199]. Copyright 2017, Optical Society of America.

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Fig. 15. Broadband mode-locked fiber laser by a large-area

{WSe}_{2}

film. (a) Schematic image of the microfiber-integrated

{WSe}_{2} - SA

fabrication process by transferring the CVD grown

{WSe}_{2}

film onto the TF. (b) SEM image of the microfiber coated with the

{WSe}_{2}

film. (c) Magnified SEM image of the marked area in (b). (d)–(g) Mode-locked characteristics of the EDFL. (d) Optical spectrum; (e) AC trace; (f) RF spectrum; (g) RF spectrum in broad bandwidth. (h)–(k) Output laser performances of the TDFL. (h) Optical spectrum; (i) AC trace; (j) RF spectrum; (k) wideband RF spectrum. (a)–(k) Reproduced with permission^[215]. Copyright 2017, Optical Society of America.

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Fig. 16. Wide-spectral mode-locking with different 2D materials.

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Gain materials	Modulation depth (%)	τ_p (fs)^(a)	λ (nm)^(b)	f_rep (MHz)^(c)	P_out (mW)^(d)	Slope efficiency (%)	Pump source^(e)	Ref.
Pr³⁺:LiYF₄	\	\	523	\	2900	79	497 DL	[104]
Ti:sapphire	\	68	816	379	200	10	InGaN DL	[105]
Yb:CNGG	0.9	55	1051.5	87	60	1	DBR DL	[106]
Yb,Na:CNGG	0.6	45	1061	104	734	68.5	980 DL	[107]
Yb:CaGdAlO₄	\	166	1050	10.6	1200	2.8	980 DL	[108]
Yb:KGW	0.5	56	1040	77.3	1950	\	980 DL	[109]
Er:Yb:glass	0.4	4700	1535	9788	9	\	980 DL	[110]
Er:Yb:glass	\	5400	1544.4	6803.3	30	\	980 DL	[111]
Tm,Ho:CaYAlO₄	\	87	2042.6	80.45	27	22	TSL	[103]
Tm:LuScO₃	1	170	1973–2142	115.2	190	33	TSL	[112]
Cr:ZnSe	\	408	2042	127	403	12.2	TDFL	[113]
Tm:(Lu_2/3Sc_1/3)₂O₃ ceramic	\	74	2057	78.9	175	34	TSL	[114]
Tm,Ho:CNGG	\	73	2061	89.3	36	\	TSL	[115]
Cr:ZnSe	\	100	2450	215	100	\	EDFL	[116]
Cr:ZnS	\	130	2375	180	130	\	EDFL	[117]
Yb:Lu₂O₃ disk	1.1	616	1033	10	82,000	44	DL	[118]
Yb:YAG disk	2.7	780	1030	10.96	210,000	\	940 DL	[119]
Yb:YAG disk	1.1	940	1030	8.88	350,000	\	DL	[85]
Yb:Lu₂O₃ disk	1.6	255	60.8	17.35	320,000	\	976 DL	[98]
VECSEL	1.4	216	1035	2770	269	2.1	DL	[89]
VECSEL	\	95	1025	2200	90	\	790 DL	[90]
VECSEL	0.5	682	1030	1710	5100	\	808 DL	[91]
VECSEL	\	400	1013	1670	3300	2.9	808 DL	[93]
VECSEL	2	5000	1341	1030	1670	\	980 DL	[120]
MIXSEL	\	570	964	101.2	127	\	808 DL	[95]
MIXSEL	\	28,100	959	2470	6400	17.3	808 DL	[96]
MIXSEL	\	144	1033	2730	30	<0.5	808 DL	[97]

Table 1. Passively Mode-Locked Solid-State Lasers Based on SESAMs.

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Gain materials	Nanomaterials	Modulation depth (%)	τ_p (ps)^(a)	λ (nm)^(b)	f_rep (MHz)^(c)	P_out (mW)^(d)	Pump source^(e)	Ref.
Ti:sapphire	SWCNT	\	0.2	810	110	45	AL	[121]
Ti:sapphire	SWCNT	0.15	0.062	800	99.4	600	532 nm DL	[122]
Yb:KLuW	SWCNT	0.25	0.115	1045	89	53	TSL	[123]
Yb:KYW/KYW	SWCNT	0.21	0.083	1038	84	24	TSL	[124]
Yb:YAG	SWCNT	\	2	1030.3	2080	322	DL	[125]
Cr:forsterite	SWCNT	0.4	0.12	1250	79.1	202	YFL	[126]
Tm:CNNGG	SWCNT	0.5	0.084	2018	89.9	22	TSL	[127]
Cr:ZnS	CNT	\	0.061	2350	250	950	EDFL	[128]
Tm:KY(WO₄)₂	PbS QD	\	\	1936	185	20	802 DL	[138]
Yb:YOCB	Graphene	\	0.152	1037	99.9	53	980 DL	[130]
Tm:CLNGG	Graphene	\	0.354	2010	98	97	790 DL	[130]
Cr:ZnSe	Graphene	\	0.116	2352	99	66	EYFL	[130]
Nd:YAG	Graphene	\	16	1064	11,500	12	809 DL	[131]
CrZnS	Graphene	\	0.041	2370	108	250	EDFL	[132]
Nd:YVO₄	MoS₂	7	12.7	1064.2	88.3	89	808 DL	[133]
Nd:LuVO₄	PtSe₂	12.6	15.8	1066.573	61.3	180	808 DL	[134]
VECSEL	SWCNT	0.25	1.23	1074	613	136	DL	[135]
VECSEL	Graphene	0.55	0.466	949	2480	26	808 DL	[136]

Table 2. Passively Mode-locked Solid-state Lasers Based on LDM-SAs

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Materials	Integration method^(a)	λ (nm)^(b)	SA properties^(c)			Laser performances^(d)				Ref.
Materials	Integration method^(a)	λ (nm)^(b)	α_s (%)	I_s (MW·cm⁻²)	α_ns (%)	τ (fs)	f_rep (MHz)	P (mW)	SNR (dB)	Ref.
SWCNT	Sandwiched	1030	15	\	44	235	50	155	\	[166]
SWCNT	Sandwiched	1030	52.7	2.512	51	175	21.2	8.68	63	[167]
SWCNT	Sandwiched	1550	17	203	\	74	33	1.2	76	[145]
CNT	Sandwiched	1928.5	13.3	\	\	501	56.368	28.5	>70	[168]
SWCNT	Sandwiched	1560	16.9	18.9	\	113	18.76	12.8	77	[169]
SWCNT	SPF	1563	\	\	\	1020	38.9	250	\	[152]
CNT	FP mirror	1563	5	2.5	\	790	19,450	\	27	[170]
SWCNT	Sandwiched	1927	10	68	14	152	25.76	4.85	73	[171]
Graphene	Sandwiched	1560	2	337	28	174	27.4	\	87.4	[172]
Graphene	Sandwiched	1550	\	\	\	263	18.67	0.68	63	[173]
Graphene	Sandwiched	1558	2	100	70	268	27.4	1.2	87.4	[174]
Graphene	FP mirror	1562	\	\	\	865	9670	\	40	[175]
MoS₂	Sandwiched	979	3.6	6.3	6.3	13,000	26.5	16.7	60	[176]
MoS₂	TF	1556.86	2.82	\	57.34	3000	2500	5.39	\	[153]
MoS₂	Sandwiched	1569.5	4.3	34	24	710	12.09	1.78	60	[177]
WS₂	Sandwiched	1572	2.9	370	30.9	919	25.3	\	75	[178]
WS₂	SPF	1557	11	5	18	660	10.2	\	65	[179]
WS₂	TF	1566	0.14	\	82	467	21.1	0.32	60.8	[180]
WS₂	TF	1561	0.5	\	21.4	369	24.93	1.93	69	[181]
WSe₂	SPF	1556.7	0.3	\	\	1310	3252.65	19	\	[182]
MoSe₂	Sandwiched	1560	7.3	\	\	580	8.8	218	50	[183]
ReS₂	Sandwiched	1557	0.12	74	\	1600	5.48	0.4	\	[184]
SnS₂	Sandwiched	1562	4.6	125	13.6	623	29.33	1.2	45	[185]
Bi₂Se₃	Sandwiched	1557	3.9	12	68	660	12.5	1.8	55	[186]
Bi₂Te₃	Sandwiched	1557	2	180	34	1080	8.64	0.11	60	[187]
Bi₂Te₃	TF	1560	1.82	\	67	2180	3125	\	\	[188]
Bi	TF	1561	5.6	48.2	62.3	193	8.8	5.6	55	[189]
BP	Sandwiched	1560.5	4.6	\	48	272	28.2	0.5	65	[190]
BP	Sandwiched (printed)	1555	10.03	14.98	9.97	102	23.9	1.7	60	[162]
BP	Sandwiched (printed)	1562	\	\	\	605	31.6	\	56	[161]
TiS₂	Sandwiched	1569.5	62	1210	\	1040	5.34	\	66	[191]
GaTe	TF	1563.17	42.3	\	7.1	408	36.5	13.2	80	[154]
GeTe	TF	1931.51	8.3	\	76.7	983	35	16.2	87.6	[154]
HfS₂	TF	1561.8	15.7	8	20.6	221.7	21.45	89.4	68	[155]
HfSe₂	TF	1561.4	5.8	163.2	45.6	297	18.09	48.5	80	[156]
AuTe₂Se_4/3	Sandwiched	1557.53	65.58	0.089	18.83	147.7	69.93	21.4	91	[150]
Ti₃CN	SPF	1557	1.7	\	\	660	15.4	0.05	60	[160]

Table 3. Passively Mode-Locked Fiber Lasers Based on LPE-SAs.

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Materials	Integration method^(a)	λ (nm)^(b)	SA Properties^(c)			Laser Performances^(d)				Ref.
Materials	Integration method^(a)	λ (nm)^(b)	α_s (%)	I_s (MW·cm⁻²)	α_ns (%)	τ (fs)	f_rep (MHz)	P (mW)	SNR (dB)	Ref.
Bi₂Te₃	TF	1562.4	6.2	28	20	320	2950	45.3	75	[193]
Bi₂Te₃	TF	1930.07	38	3.3	31.2	1240	14.51	130	84	[195]
Bi₂Te₃	TF	1542	7.42	175	\	70	95.4	63	65	[200]
Bi₂Te₃	SPF	1047.1	0.5-2.9	\	\	5900	19.28	4	71	[201]
Bi₂Te₃	SPF	1558	5.3-13	\	\	167	25.38	5.34	68	[194]
WTe₂	TF	1915.5	31	7.6	34.3	1250	18.72	39.9	95	[197]
MoTe₂	TF	1559.57	25.5	9.6	19.1	229	26.6	57	93	[196]
		1934.85	22.1	12.3	21.3	1300	15.37	212	84	[196]
α-In₂Se₃	TF	1565	4.5	7.3	21.9	276	40.9	83.2	90	[202]
		1932	6.9	10.6	28.8	1020	15.8	112.4	90	[202]
WS₂	TF	1559.7	1.2	25	\	452	1040	11.3	48	[203]
WS₂	SAM	1549.98	4.48	138	2	\	396	6.2	56.3	[198]
WS₂/MoS₂/WS₂	SAM	1562.66	16.99	6.23	36.97	296	36.46	25	90.3	[199]
MoS₂-Bi₂Te₃-MoS₂	SAM	1554	64.17	151.176	35.83	286	36.4	20	73	[204]
Cd₃As₂	Sandwiched	1968.5	3.5	12	\	1360	23.2	4.9	70	[205]
		1560	5.1	67	\	920	17.6	0.7	70	[205]

Table 4. Passively Mode-Locked Fiber Lasers Based on PVD-SAs.

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Materials	Integration method^(a)	λ (nm)^(b)	SA properties^(c)			Laser performances^(d)				Ref.
Materials	Integration method^(a)	λ (nm)^(b)	α_s (%)	I_s (MW·cm⁻²)	α_ns (%)	τ (fs)	f_rep (MHz)	P (mW)	SNR (dB)	Ref.
Graphene	Sandwiched	1545	11	\	∼64	88	21.15	1.5	65	[206]
Graphene	Sandwiched	1884	0.4	\	\	1200	20.5	1.35	∼70	[207]
Graphene	TF	1550	12	40	27	970	8.57	\	65	[208]
MoS₂	Sandwiched	1568.9	35.4	0.35	34.1	1280	8.288	5.1	62	[209]
MoS₂	Sandwiched	1569.6	\	\	\	1420	216	6.81	36.1	[70]
WS₂	Sandwiched	1568.3	15.1	157.6	45.9	1490	0.487	62.5	71.8	[210]
WS₂	TF	1565	0.5	\	\	332	31.11	\	81.6	[211]
MoSe₂	TF	1552	22.57	7.747	46.46	207	64.56	\	85	[212]
WSe₂	Sandwiched	1562	52.38	1.399	45.51	185	58.8	30	95	[213]
WSe₂	TF	1863.96	1.83	3.7	87	1160	11.36	32.5	53	[214]
WSe₂	TF	1556.42	54.5	2.97	∼10	477	14.02	\	80	[215]
WSe₂	TF	1886.22	1.83	\	∼90	1180	11.36	32.5	80	[215]
MoTe₂	TF	1930.22	5.7	8.3	70	952	14.353	36.7	87.8	[216]
PtSe₂	TF	1563	4.9	340	∼70	1020	23.3	\	61	[217]
Bi₂Se₃	Sandwiched	1557.9	15	6.59	\	\	1.71	82.6	42	[218]

Table 5. Passively Mode-locked Fiber Lasers Based on CVD-SAs

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Mengyu Zhang, Hao Chen, Jinde Yin, Jintao Wang, Jinzhang Wang, Peiguang Yan. Recent development of saturable absorbers for ultrafast lasers [Invited][J]. Chinese Optics Letters, 2021, 19(8): 081405

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