A novel spectral shaping mechanism for pre-compensating gain-narrowing is investigated numerically and experimentally. The spectral shaping is realized based on the mapping between the frequency and time domain, via the modulation of intensity in time domain can be casted to frequency domain. The optical ultrashort pulse is injected to a nonlinear amplifying loop mirror (NALM) and modulated both in the frequency and time domain. The pulse spectrum can be modulated in saddle-shape, and the sinking depth of spectrum can be tuning with the variation of the pump power of the NALM, which can pre-compensate the gain-narrowing and sustain a broadband spectrum in later high-gain amplifier. A proof-of-principle experiment is carried out. The spectral bandwidth of amplified optical pulse increases from about 10 nm to 19 nm, and pulse duration is shorten from 669 fs to 342 fs with the implementation of NALM spectral shaper, which shows a significant suppressing on the spectral gain-narrowing. This tunable NALM spectral shaper is employed with an all-polarization-maintaining (PM) and all-fiber structure, providing a flexible and practical solution to overcome gain-narrowing in high-gain amplifications.
In this study, different colors with a large variation in color gamut were induced by 1064 nm nanosecond pulsed laser on TC4. Then, we tested the stability and durability of the color marking made by nanosecond pulsed laser under various chemical agents and aggressive temperature conditions. The results showed that colors marking on TC4 have high sustainability to acidic and neutral solutions and also can stand the high temperature. Due to the high stability and durability of the induced colors, it is not easy to secondarily revise the colored areas, which will reduce the applicability of laser coloring technology. Here, we proposed using ultrafast pulsed laser to selectively erase the colored areas in ethanol and nitrogen atmosphere. We found that ultrafast pulsed laser had high erasing quality on the colored surface. The ΔE* before and after erasing is less than 7, and the reflectance spectra of erased areas is similar to the untreated areas. These results are essential to provide a proper solution for the lack of applicability and flexibility in laser coloring technology, which can open new perspectives in industrial applications.
In this work, we used 1064 nm nanosecond pulsed laser irradiating titanium surface to obtain different colors with a large variation in total color difference (ΔE*) and systematized the color gamut on titanium. A hand-held colorimeter and the CIEL*a*b* color difference formula were used to quantitatively evaluate the influences of process parameters on the color changes of titanium surfaces. Moreover, a method was reported in this paper to erase selectively the colored areas by changing the processing atmosphere. We compared the erasing effects between ultrafast pulsed laser and nanosecond pulsed laser, and found that ultrafast pulsed laser has higher quality erasure on the colored surface. The results showed that more than 90% O element of colored areas were erased and Ti element increased quickly. The ΔE* between erased areas and bare materials is less than 7, and the reflectance spectra of erased areas is similar to the untreated areas. Furthermore, the wettability of erased fields was changed and the contact angle (CA) was <10°, which indicates the surface shows superhydrophilicity in air.
In this work, different colors with a large variation in total color difference (ΔE*) were induced by 1064 nm nanosecond pulsed laser on TC4 titanium alloy, which can expand and systematize the color gamut on TC4. The influences of laser parameters on the color difference were evaluated by hand-held colorimeter with CIEL*a*b* color space quantitatively and the morphology of oxide thin film was characterized. With the increasing of scanning speed, ΔE* increased from 22.8 to 95.72 and lightness difference (ΔL*) increased from 13 to 78. With the increasing of laser power, ΔL* decreased gradually. With the increasing of pulse repetition frequency, ΔE* increased from 15.07 to 98.42, and ΔL* increased from -9 to 74. Finally, the experiment of color erasing and repairing in controllable processing atmosphere was carried out as well. The ΔE* before and after laser erasing is less than 7 in low oxygen environment by introducing nitrogen atmosphere, and being exposed to liquids, which indicates that colors can be erased and repaired based on laser induced reduction. Rewriting in the erased fields can increase the saturation and lightness of colors. The possibility of erasing or rewriting colors in special treatment environment would take laser coloring to a new level, allowing not only improvement of color quality from reprocessed fields but also modification of marks during the laser processing according to the wishes of operators.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.