Atlantic Research Corp., the Alexandria technology company, yesterday announced a 25 percent rise in 1980 profits, which rose to $2.3 million ($1.36 a share) last year compared with $1.8 million ($1.41) for 1979.

Sales rose by 40 percent in 1980, jumping from $57.7 million in 1979 to $80.5 million last year.

For the 1980 fourth quarter, profits rose to $640,000 (35 cents) from $592,000 (41 cents), while sales jumped from $18 million in 1979 to $25 million in 1980.

The company said earnings per share dropped as the result of a May 1980 sale of 400,000 shares, raising the number of outstanding shares from an average in 1979 of 1.3 million to a 1980 average of 1.69 million.

In other reports, the Federal Home Loan Mortgage Corp. reported profits of $33.6 million for 1980, down from $35.6 million in 1979. At the end of 1980, the corporation's capital base was $482.6 million, compared with $437.6 million at the end of 1979.

Government Employees Financial Corp. reported a 1980 loss of $1.4 million compared with a 1979 profit of $2.04 million ($1.33 a share). Income fell from $42.4 million in 1979 to $39.5 million last year.

For the fourth quarter, the company reported a loss of $240,000 compared with profits of $150,000 (7 cents) last year.

The company said the loss was a result of increasing provisions for loss expense during the third quarter, record loan write-offs, the national economic picture and implementation of new federal bankruptcy laws.

Fair Lanes Inc. has reported a slight rise in second-quarter profits, which rose $1.58 million (35 cents a share) for the quarter ended Dec. 31 from 1979 second-quarter profits of $1.51 million (31 cents).

For the first six months of the fiscal year, profits rose from $1.59 million (33 cents) to $1.6 million (36 cents).

Isomet Corp. of Springfield reported 1980 profits of $846,000 (59 cents a share), up from $149,000 (11 cents) in 1979, as sales rose from $2.3 million in 1979 to $3.4 million last year.

United Savings & Loan, based in Vienna, reported 1980 profits of $432,067 ($1.23 a share) up from $413,318 ($1.18) in 1979. Total assets rose to $70 million compared with $65.1 million for 1979.

Universal Security Instruments, an Owings Mills company, reported a 252 percent increase in profits for the fiscal quarter ended Dec. 31. Profits for the quarter rose to $290,155 (10 cents a share), up from $93,690 (3 cents) for the same quarter last year.