From The University of Rochester
5.22.24
Luke Auburn
University of Rochester researchers created a chip-scale microcomb laser with an innovative design that allows users to control the optical frequency comb simply by switching on a power source. Credit: University of Rochester / J. Adam Fenster
Lasers developed at the University of Rochester offer a new path for on-chip frequency comb generators.
Light measurement devices called optical frequency combs have revolutionized metrology, spectroscopy, atomic clocks, and other applications. Yet challenges with developing frequency comb generators at a microchip scale have limited their use in everyday technologies such as handheld electronics.
In a study published in Nature Communications, researchers at the University of Rochester describe new microcomb lasers they have developed that overcome previous limitations and feature a simple design that could open the door to a broad range of uses.
Fig. 1: Device concept of the integrated comb laser.
a Conceptual illustration of the comb generation and mode-locking principle, in which electro-optic (EO) comb generation, Kerr comb generation, and broadband optical gain all work synergistically together inside a single laser cavity for on-demand generation of mode-locked soliton comb. In addition, the laser comb output is detected and fed back to the laser cavity for resonant EO modulation to realize a self-sustained operation. b Schematic of comb laser cavity structure formed by hybrid integration between a RSOA chip and a LN external cavity chip. Two different configurations are employed: A, cavity-enhanced (CE) comb laser structure in which the LN external cavity is formed mainly by an embedded high-Q racetrack resonator together with a broadband Sagnacloop mirror; B, Fabry-Perot (FP) comb laser in which the LN external cavity is formed by an EO phase modulation section together with an a broadband Sagnac loop mirror. c Photo of a CE comb laser, showing that the RSOA is edge-coupled to the LN external cavity chip. d Zoom-in photo showing the edge-coupling region between the RSOA and the LN chip. e Photo of the racetrack resonator and the loop mirror in a CE comb laser. f Photo of the EO phase modulator and the loop mirror in an FP comb laser.
See the science paper for further instructive material with images.
What are microcombs?
Optical frequency combs generate a spectrum of light consisting of multiple coherent beams, each tuned to a different frequency or color, in evenly spaced distances. The resulting shape resembles the teeth on a hair comb. In recent years, scientists have been working to create miniaturized versions of this technology, or microcombs, that can fit on small chips.
But while scientists have made progress in prototyping microcombs, they have had limited success producing viable versions that can be applied in practical devices. Obstacles include low power efficiency, limited controllability, slow mechanical responses, and the need for sophisticated system pre-configuration.
A simplified approach
A team of researchers led by Qiang Lin, a professor in Rochester’s Department of Electrical and Computer Engineering and at the Institute of Optics, created a unique approach to solve these challenges in a single device.
According to Jingwei Ling, an electrical and computer engineering PhD student in Lin’s lab and the lead author of the paper, previous approaches usually rely on a single-wavelength laser injected into a nonlinear converter that can transfer the single wavelength into multiple wavelengths, forming the optical comb.
ONE-STOP SHOP: Electrical and computer engineering PhD student Zhengdong Gao adjusts a new “all in one” microcomb laser device created in the lab of professor Qiang Lin. (University of Rochester photo / J. Adam Fenster)
“We eliminated the single wavelength because that’s going to degrade the system’s efficiency,” says Ling. “We instead have all the comb itself being amplified in a feedback loop inside the system, so all the wavelengths get reflected and enhanced inside a single element.”
The simplicity of the “all in one” microcomb laser results in lower power demands, lower costs, high tunability, and a turnkey operation.
“It is easy to operate,” says coauthor Zhengdong Gao, also an electrical and computer engineering PhD student in Lin’s lab. “The previous methods make it hard to excite the comb, but with this method we only need to switch on the power source, and we can control the comb directly.”
Hurdles remain for implementing these microcomb lasers, particularly with developing fabrication techniques to create such tiny components within the tolerances necessary for manufacturing. But the researchers are hopeful that their devices can be used for applications such as telecommunications systems and light detection and ranging (LiDAR) for autonomous vehicles.
The Defense Advanced Research Projects Agency and the National Science Foundation supported this research.
See the full article here .
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The University of Rochester is a private research university in Rochester, New York. The university grants undergraduate and graduate degrees, including doctoral and professional degrees.
The University of Rochester enrolls approximately 6,800 undergraduates and 5,000 graduate students. Its 158 buildings house over 200 academic majors. The University of Rochester is the 7th largest employer in the Finger lakes region of New York.
The College of Arts, Sciences, and Engineering is home to departments and divisions of note. The Institute of Optics was founded in 1929 through a grant from Eastman Kodak and Bausch and Lomb as the first educational program in the US devoted exclusively to Optics and awards approximately half of all Optics degrees nationwide and is widely regarded as the premier Optics program in the nation and among the best in the world.
The Departments of Political Science and Economics have made a significant and consistent impact on positivist social science since the 1960s and historically rank in the top 5 in their fields. The Department of Chemistry is noted for its contributions to synthetic Organic Chemistry, including the first lab-based synthesis of morphine. The Rossell Hope Robbins Library serves as The University of Rochester’s resource for Old and Middle English texts and expertise. The university is also home to Rochester’s Laboratory for Laser Energetics, a Department of Energy supported national laboratory.
The University of Rochester’s Eastman School of Music ranks high among undergraduate music schools in the U.S. The Sibley Music Library at Eastman is the largest academic music library in North America and holds the third largest collection in the United States.
In its history The University of Rochester alumni and faculty have earned Nobel Prizes; Pulitzer Prizes; Grammy Awards; Guggenheim Awards; there are members of National Academy of Sciences; National Academy of Engineering; National Academy of Inventors; and National Academy of Inventors Hall of Fame; and Rhodes Scholarships.
Early history
The University of Rochester traces its origins to The First Baptist Church of Hamilton (New York) which was founded in 1796. The church established the Baptist Education Society of the State of New York later renamed the Hamilton Literary and Theological Institution in 1817. This institution gave birth to both Colgate University and the University of Rochester. Its function was to train clergy in the Baptist tradition. When it aspired to grant higher degrees, it created a collegiate division separate from the theological division.
The collegiate division was granted a charter by the State of New York in 1846 after which its name was changed to Madison University. John Wilder and the Baptist Education Society urged that the new university be moved to Rochester, New York. However, legal action prevented the move. In response, dissenting faculty, students, and trustees defected and departed for Rochester, where they sought a new charter for a new university.
Madison University was eventually renamed as Colgate University.
Founding
Asahel C. Kendrick- professor of Greek- was among the faculty that departed Madison University for The University of Rochester. Kendrick served as acting president while a national search was conducted. He reprised this role until 1853 when Martin Brewer Anderson of the Newton Theological Seminary in Massachusetts was selected to fill the inaugural posting.
The University of Rochester’s new charter was awarded by the Regents of the State of New York on January 31, 1850. The charter stipulated that The University of Rochester have $100,000 in endowment within five years upon which the charter would be reaffirmed. An initial gift of $10,000 was pledged by John Wilder which helped catalyze significant gifts from individuals and institutions.
Classes began that November with approximately 60 students enrolled including 28 transfers from Madison. From 1850 to 1862 the university was housed in the old United States Hotel in downtown Rochester on Buffalo Street near Elizabeth Street- today West Main Street near the I-490 overpass. On a February 1851 visit Ralph Waldo Emerson said of the university:
“They had bought a hotel, once a railroad terminus depot, for $8,500, turned the dining room into a chapel by putting up a pulpit on one side, made the barroom into a Pythologian Society’s Hall, & the chambers into Recitation rooms, Libraries, & professors’ apartments, all for $700 a year. They had brought an omnibus load of professors down from Madison bag and baggage… called in a painter and sent him up the ladder to paint the title “University of Rochester” on the wall, and they had runners on the road to catch students. And they are confident of graduating a class of ten by the time green peas are ripe.”
For the next 10 years The University of Rochester expanded its scope and secured its future through an expanding endowment; student body; and faculty. In parallel a gift of 8 acres of farmland from local businessman and Congressman Azariah Boody secured the first campus of The University of Rochester upon which Anderson Hall was constructed and dedicated in 1862. Over the next sixty years this Prince Street Campus grew by a further 17 acres and was developed to include fraternity houses; dormitories; and academic buildings including Anderson Hall; Sibley Library; Eastman and Carnegie Laboratories the Memorial Art Gallery and Cutler Union.
Twentieth century
Coeducation
The first female students were admitted in 1900- the result of an effort led by Susan B. Anthony and Helen Barrett Montgomery. During the 1890s a number of women took classes and labs at The University of Rochester as “visitors” but were not officially enrolled nor were their records included in the college register. President David Jayne Hill allowed the first woman- Helen E. Wilkinson- to enroll as a normal student although she was not allowed to matriculate or to pursue a degree. Thirty-three women enrolled among the first class in 1900 and Ella S. Wilcoxen was the first to receive a degree in 1901. The first female member of the faculty was Elizabeth Denio who retired as Professor Emeritus in 1917. Male students moved to River Campus upon its completion in 1930 while the female students remained on the Prince Street campus until 1955.
Expansion
Major growth occurred under the leadership of Benjamin Rush Rhees over his 1900-1935 tenure. During this period George Eastman became a major donor giving more than $50 million to the university during his life. Under the patronage of Eastman, the Eastman School of Music was created in 1921. In 1925 at the behest of the General Education Board and with significant support for John D. Rockefeller George Eastman and Henry A. Strong’s family medical and dental schools were created. The university award its first Ph.D that same year.
During World War II The University of Rochester was one of 131 colleges and universities nationally that took part in the V-12 Navy College Training Program which offered students a path to a Navy commission. In 1942, The University of Rochester was invited to join the Association of American Universities as an affiliate member and it was made a full member by 1944. Between 1946 and 1947 in infamous uranium experiments researchers at the university injected uranium-234 and uranium-235 into six people to study how much uranium their kidneys could tolerate before becoming damaged.
In 1955 the separate colleges for men and women were merged into The College on the River Campus. In 1958 three new schools were created in engineering, business administration and education. The Graduate School of Management was named after William E. Simon- former Secretary of the Treasury in 1986. He committed significant funds to the school because of his belief in the school’s free market philosophy and grounding in economic analysis.
Financial decline and name change controversy
Following the princely gifts given throughout his life George Eastman left the entirety of his estate to The University of Rochester after his death by suicide. The total of these gifts surpassed $100 million before inflation and as such The University of Rochester enjoyed a privileged position amongst the most well endowed universities. The University of Rochester’s financial position has ranked third, near Harvard University’s endowment and the University of Texas System’s Permanent University Fund . Due to a decline in the value of large investments and a lack of portfolio diversity The University of Rochester ‘s place dropped to the top 25 by the end of the 1980s. At the same time the preeminence of the city of Rochester’s major employers began to decline.
In response The University of Rochester commissioned a study to determine if the name of the institution should be changed to “Eastman University” or “Eastman Rochester University”. The study concluded a name change could be beneficial because the use of a place name in the title led respondents to incorrectly believe it was a public university, and because the name “Rochester” connoted a “cold and distant outpost.” Reports of the latter conclusion led to controversy and criticism in the Rochester community. Ultimately, the name “The University of Rochester” was retained.
Renaissance Plan
In 1995 The University of Rochester president Thomas H. Jackson announced the launch of a “Renaissance Plan” for The University of Rochester that reduced enrollment from 4,500 to 3,600 creating a more selective admissions process. The plan also revised the undergraduate curriculum significantly creating the current system with only one required course and only a few distribution requirements known as clusters. Part of this plan called for the end of graduate doctoral studies in Chemical Engineering; comparative literature; linguistics; and Mathematics, the last of which was met by national outcry. The plan was largely scrapped and Mathematics exists as a graduate course of study to this day.
Twenty-first century
Meliora Challenge
Shortly after taking office university president Joel Seligman commenced the private phase of the “Meliora Challenge”- a $1.2 billion capital campaign- in 2005. The campaign reached its goal in 2015- a year before the campaign was slated to conclude. In 2016, The University of Rochester announced the Meliora Challenge had exceeded its goal and surpassed $1.36 billion. These funds were allocated to support over 100 new endowed faculty positions and nearly 400 new scholarships.
The Mangelsdorf Years
On December 17, 2018 The University of Rochester announced that Sarah C. Mangelsdorf would succeed Richard Feldman as President of the University. Her term started in July 2019 with a formal inauguration following in October during Meliora Weekend. Mangelsdorf is the first woman to serve as President of the University and the first person with a degree in psychology to be appointed to Rochester’s highest office.
In 2019 students from China mobilized by the Chinese Students and Scholars Association (CSSA) defaced murals in the University’s access tunnels which had expressed support for the 2019 Hong Kong Protests, condemned the oppression of the Uighurs, and advocated for Taiwanese independence. The act was widely seen as a continuation of overseas censorship of Chinese issues. In response a large group of students recreated the original murals. There have also been calls for Chinese government run CSSA to be banned from campus.
Research
The University of Rochester is a member of the Association of American Universities and is classified among “R1: Doctoral Universities – Very High Research Activity”.
Rochester has ranked very highly nationally in research spending.
Some of the major research centers include the Laboratory for Laser Energetics, a laser-based nuclear fusion facility, and the extensive research facilities at the University of Rochester Medical Center.
Recently The University of Rochester has also engaged in a series of new initiatives to expand its programs in Biomedical Engineering and Optics including the construction of the new $37 million Robert B. Goergen Hall for Biomedical Engineering and Optics on the River Campus.
Other new research initiatives include a cancer stem cell program and a Clinical and Translational Sciences Institute. The University of Rochester also has the ninth highest technology revenue among U.S. higher education institutions. Notable patents include Zoloft and Gardasil. WeBWorK, a web-based system for checking homework and providing immediate feedback for students was developed by The University of Rochester professors Gage and Pizer. The system is now in use at over 800 universities and colleges as well as several secondary and primary schools. The University of Rochester scientists work in diverse areas. For example, physicists developed a technique for etching metal surfaces such as platinum; titanium; and brass with powerful lasers enabling self-cleaning surfaces that repel water droplets and will not rust if tilted at a 4 degree angle; and medical researchers are exploring how brains rid themselves of toxic waste during sleep.
sciencesprings 